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Antibiotics in the food chain: Their impact on the consumer
Abstract
: The development of resistance to antibiotics by pathogenic bacteria is a problem of increasing concern, resulting in treatment failures and longer periods of morbidity. Resistant bacteria may emerge following exposure of bacterial populations to sublethal concentrations of antibiotics. This can occur as a result of antibiotic use in clinical and veterinary practice and in agriculture. Antibiotics are used widely in agriculture and aquaculture for therapeutic, prophylactic and growth-promoting purposes; residual antibiotics remaining in the flesh at the time of slaughter may result in direct exposure of the consumer to these drugs. In addition, the presence of low levels of antibiotic may select for resistant bacteria in the intestines of animals intended for human consumption. There is now strong evidence that the use of antibiotics during the production of food animals can lead to the exposure of consumers to antibiotic-resistant bacteria. Control measures are being introduced in the developed world to limit the use of clinically important antibiotics as growth promoters. However, this is not yet taking place in many developing countries. With increasing globalisation of our food market, an international approach to the control of antibiotic use is essential.
(C) 2000 Lippincott Williams & Wilkins
(C) 2000 Lippincott Williams & Wilkins, Inc.
... In the developing world, multi-resistant bacteria to various antibiotics is becoming very big problem in the treatment of diseases (Willis, 2000). ...
... The EU banned avoparcin in 1997 and four growth promoters, spiramycin, tylosin phosphate, virginiamycin and zinc bacitracin. The Danish Food Industry stopped the use of all antimicrobials for growth promotion in 1998 (Willis, 2000). In 2005, Food and Drug Administration (FDA) banned the use of enrofloxacin in food animals due to the increased levels of fluoroquinolone-resistant Campylobcter spp. ...
... In fact, antibiotics is excreted to the urine in humans and animals. Therefore, antibiotics may also enter water courses from farm waste, allowing the possibility for further selection of resistant organisms (Willis, 2000). ...
... As the global population exceeds the 7 billion mark (U.S. Census Bureau, 2016), the demand for inexpensive, plentiful, wholesome, and safe food products has never been louder or more urgent ( Tilman et al., 2002;OECD/FAO, 2015;Peter et al., 2013). The generalized concern over the efficiency of the current food production system has led the public to give additional attention to agricultural production and to question practices that are perceived as unsafe for the animals, the environment, or to human health ( Bruhn, 1999;Willis, 2000;Gorback, 2001;Tilman et al., 2002;Lusk et al., 2007). One such practice that has especially attracted the public's attention is the exposure to chemical compounds, such as environmental pollutants, pesticides, and antibiotics in agricultural settings, and their potential presence as residues in food products ( Bruhn, 1999;NRC, 1999;Resurreccion and Galvez, 1999;Willis, 2000;Verbeke et al., 2007). ...
... The generalized concern over the efficiency of the current food production system has led the public to give additional attention to agricultural production and to question practices that are perceived as unsafe for the animals, the environment, or to human health ( Bruhn, 1999;Willis, 2000;Gorback, 2001;Tilman et al., 2002;Lusk et al., 2007). One such practice that has especially attracted the public's attention is the exposure to chemical compounds, such as environmental pollutants, pesticides, and antibiotics in agricultural settings, and their potential presence as residues in food products ( Bruhn, 1999;NRC, 1999;Resurreccion and Galvez, 1999;Willis, 2000;Verbeke et al., 2007). This concern has led consumers to consider erroneously the exposure to chemicals in foods as one of the top 10 causes of death ( Nicholls et al., 1994). ...
... Unfortunately, some of these compounds have the potential to form residual deposits of pharmacologically active compounds in edible tissues and other food products, which can lead to potential deleterious health issues in consumers ( Paige et al., 1997;Cerniglia and Kotarski, 1999;Donoghue, 2003). Thus it is important that producers, veterinarians, and all involved in food production are aware and follow the approved labeling instructions for the drugs, to protect consumers from potentially harmful concentrations of residues in animal food products ( Anadon and MartinezLarra~ naga, 1999;Willis, 2000). ...
Poultry products are one of the most important sources of protein food in the world. Even though it is considered a healthy meat type, there are wide concerns regarding chemical contamination in these products. This review will describe some potential chemical contaminants in poultry meat and eggs and briefly discuss the regulatory process used in the United States for the control of these contaminants as an example of prevention and control strategies used around the world.
... Antimicrobial agents are commonly applied in the animal breeding industry to effectively prevent or treat disease outbreaks caused by pathogenic organism. Never-theless, the extensive use of drugs in aquaculture has contributed to the development of antibiotic-resistant bacteria and posed serious problems in aquatic ecosystems (1,17,40). Water contaminated with industrial pollutants such as heavy metals may enhance selection for antibiotic resistance and vice versa (4,7,26). The exchange of resistance genes between foodborne and human gastrointestinal tract microflora has been recognized as a potential threat to human health (40). ...
... Water contaminated with industrial pollutants such as heavy metals may enhance selection for antibiotic resistance and vice versa (4,7,26). The exchange of resistance genes between foodborne and human gastrointestinal tract microflora has been recognized as a potential threat to human health (40). ...
Vibrio parahaemolyticus can cause serious human seafoodborne gastroenteritis and even death. In this study, we isolated and characterized 208 V. parahaemolyticus strains from 10 species of commonly consumed crustaceans and shellfish available in fish markets in Shanghai, People's Republic of China, in 2014. Most of these aquatic species had not been detected previously. The results revealed an extremely low occurrence of pathogenic V. parahaemolyticus carrying the toxin gene trh (1.9%). However, a high level of resistance to the antibiotics ampicillin (94.2%), rifampin (93.3%), and streptomycin (77.9%) was found. Approximately 74.5% of the isolates had multidrug-resistant phenotypes. Tolerance to the heavy metals Cu2+, Pb2+, and Cd2+ was detected in the majority of antibiotic resistant isolates. The resistance patterns differed depending on the tested samples. The crustaceans Penaeus monodon and Marsupenaeus japonicus harbored more antibiotic-resistant bacteria, whereas the isolates from the crustacean Litopenaeus vannamei and the shellfish Busycon canaliculatus had high tolerance to eight heavy metals tested. In contrast to the wide distribution of multidrug resistance and tolerance to heavy metals, lower percentages of plasmid DNA (22.6%) and SXT/R391-like integrative and conjugative elements (4.8%) were detected in the isolates, suggesting that V. parahaemolyticus in these aquatic species may have adopted some other molecular mechanisms that mediated the high prevalence of resistance determinants. The results of this study support the need for food safety risk assessment of aquatic products.
... Monotherapy is the process of using a single method or treatment such as drug therapy to tackle and attempt to treat a condition or disorder. Use of monotherapy as opposed to combination therapy favours selection of resistance in certain infections [35,36]. In 2007, WHO member states adopted world health Assembly resolution which calls for a progressive removal of oral artemisinin-based monotherapies from market. ...
... Consequently, treating diseases caused by these resistant bacteria in humans with available antibiotics will be counterproductive and expensive [37,39]. Also, the emergence of vancomycin-resistant enterococci (VRE) is a good example of resistant bacteria in animals that humans are susceptible to [36]. A report has shown that the use of antimicrobials in agriculture is responsible for the development of resistance in these bacteria [37]. ...
The hope raised by the discovery of antibiotics has been marred by the emergence of antibiotic resistance. The major reason for this is the inappropriate use of antibiotics due to a lack of uniform policy and disregard to hospital infection control practices. Bacterial infections increase the morbidity and mortality, increase the cost of treatment, and prolong hospital stay adding to the economical burden on the nation. The problem is further compounded by the lack of education and “over the counter” availability of antibiotics in developing countries where no one really has a good idea of the extent of antibiotic resistance, because it hasn’t been monitored in a coordinated fashion and there is no good national system to test for antibiotic resistance. This menace can be managed by a lot of concerted efforts with only a few prescribed in this review study.
... The EU banned avoparcin in 1997 and four growth promoters, spiramycin, tylosin phosphate virginiamycin, and zinc bacitracin. The Danish food industry stopped the use of all antimicrobials for growth promotion in 1998 (Willis 2000). In 2005, FDA identified fluoroquinolone-resistant Campylobacter spp. ...
Antibiotics, which have been used for many years to treat infections, also play an important role in food contamination with antibiotic residues. There is also unnecessary use of antibiotics, particularly to increase production efficiency. Non-compliance with withdrawal periods and maximum residue limits (MRLs) for antibiotics used in food-producing animals results in undesirable events, such as allergic reactions, teratogenicity, carcinogenicity, changes in the microbiota and, in particular, antibiotic resistance. Therefore, it may be useful to avoid unnecessary use of antibiotics, to limit the use of antibiotics and to turn to alternatives that can be used instead of antibiotics. The aim of this review is to provide information on the undesirable effects of antibiotic residues in food-producing organisms and in the environment, their determination, and the precautions that can be taken.
... These findings are consistent with findings in Tanzania, Kuwait, Malaysia, Serbia, and the USA [28] [36] [37] [38]. The improper disposal of EUM through sinks, dustbins, and toilets as observed in the current study is environmentally unfriendly and may be linked to deleterious environmental effects [39], harmful effects on aquatic organisms [40], negative effects on public health through drinking contaminated water [41], and antimicrobial resistance [42]. The impact of improperly discarding EUM on the emergence of antimicrobial resistance in Zambia should not be disregarded, as research has linked inappropriate disposal of antibiotics to resistance [43]. ...
Background: Handling of medicines is a day-to-day activity by patients and many health care providers. However, multiple studies have brought to light inappropriate disposal methods for expired and unused medication (EUM). Improper disposal of expired and unused medicines is hazardous both to humans and the environment. Objective: This sought to measure patients’ knowledge, attitude, and practices on disposal methods of EUM. Methods: A cross-sectional study was carried out among 384 patients at three outpatient pharmacies at the University Teaching Hospitals (UTHs). The structured questionnaire was used to collect data and STAT version 15.1 was used to analyse the data. Results: 384 respondents participated in this study and, at some point, had EUM. In this study, 356 (92.7%) of the participants reported that they had never heard of a drug take-back system. Most of the participants 285 (74.2%) and 239 (62.2%) kept and donated their unused medicine, respectively. Additionally, 244 (63.5%), 212 (55.2%), and 176 (44.8%) of the participants disposed of expired medicines in the bin or garbage, flushed them in toilets or sinks, or burned them, respectively. Occupation was significantly associated with unsafe disposal of unused medicine [P-value = 0.019]. Conclusion and Relevance: Knowledge of safe disposal methods for EUM was good amongst most participants. However, used unsafe disposal methods. The majority of the participants exhibited positive attitude concerning safe disposal methods. This study highlights the need for drug-take-back program creation in Zambia.
... In addition, antibiotics are used in agriculture, aquaculture and animal husbandry to prevent infection and increase yield. The exposure of antibiotic residues from food could lead to the development of antibiotic resistant bacteria that progressively increase mortality from multidrug-resistant bacterial infections, thereby posing a tremendous threat to public health 37,38 . In our studies we observed a marginal increase in colon length in mice provided antibiotics compared to standard diet alone (30 days). ...
Ulcerative colitis (UC) is an idiopathic disease of the large intestine linked to high fat-high protein diets, a dysbiotic microbiome, and a metabolome linked to diet and/or aberrant circadian rhythms associated with poor sleeping patterns. Understanding diet-affected factors that negatively influence colonic health may offer new insights into how to prevent UC and enhance the efficacy of UC immunotherapy. In this preclinical study, we found that standard or high fiber diets in mice positively influenced their colonic health, whereas a high fat-high protein diet negatively influenced colonic health, consistent with clinical findings. Animals fed a high fat/high protein diet experienced obesity and a reduced colon length, illustrating a phenotype we suggest calling peinosis [hunger-like-condition; Greek, peina: hunger; osis: condition], as marked by a lack of nutrient energy remaining in fecal pellets. Notably, a high fat/high protein diet also led to signs of muscle weakness that could not be explained fully by weight gain. In contrast, mice on a high fiber diet ranked highest compared to other diets in terms of colon length and lack of muscle weakness. That said, mice on a high fiber diet were more prone to UC and toxic responses to immunotherapy, consistent with clinical observations. Recent studies have suggested that a standard diet may be needed to support the efficacy of immunotherapeutic drugs used to prevent and treat UC. Here we observed that protection against UC by Bin1 mAb, a passive UC immunotherapy that acts by coordinately enforcing intestinal barrier function, protecting enteric neurons, and normalizing the microbiome, was associated with increased colonic levels of healthful short-chain fatty acids (SCFA), particularly butyric acid and propionic acid, which help enforce intestinal barrier function. This work offers a preclinical platform to investigate how diet affects UC immunotherapy and the potential of dietary SCFA supplements to enhance it. Further, it suggests that the beneficial effects of passive immunotherapy by Bin1 mAb in UC treatment may be mediated to some extent by promoting increased levels of healthful SCFA. The major inflammatory bowel diseases (IBD) include Crohn's disease and Ulcerative colitis (UC). Crohn's disease is characterized by inflammation and ulceration of both the small and large intestines, whereas UC is characterized by ulceration of the large intestine (colon). UC is an idiopathic inflammatory disease of the colon that starts in the rectum and extends proximally. While the basis for its patterns of etiology, pathophysiology and progression remain poorly understood 1-5 , a variety of environmental factors contribute to UC development, including altered circadian rhythms 6,7 , high fat/high protein diets 8,9 , alcohol abuse 10,11 , and dysbiotic microbiomes plus their associated metabolomes 12. In UC patients, smoking further increases the risk of cancer and mortality in UC patients 13. Gaining deeper understanding of the dietary factors that influence and enforce colonic health is important to learn how to reduce UC risk and flares. While immunotherapies to treat UC and prevent UC flares continue to be developed, recent studies suggest that their efficacy may be influenced by dietary factors. Accordingly, there is a need for models to investigate and identify these factors, with the goal of learning how to maximize the efficacy of such immunotherapeutic agents. We have investigated the Bin1 monoclonal antibody 99D (Bin1 mAb) as a highly active passive immuno-therapy to prevent chemically-induced UC in mouse models 1-3. Bin1 is one of two BAR adapter encoding genes conserved throughout eukaryotic evolution, expressed in complex patterns of alternately spliced cytoplasmic or OPEN
... Exposure to chemical compounds, such as organic toxins, pesticides and antibiotics, in farming ecosystems and their possible existence as residues in food products are one concern that has drawn the public's interest in particular. (Bruhn 1999 [5] ; NRC 1999; Resurreccion and Galvez 1999 [37] ; Willis 2000 [44] ; Verbeke et al. 2007). This concern has led consumers to consider (erroneously) that exposure to chemicals in foods is one of the top ten causes of death (Nicholls et al. 1994) [28] . ...
... 3,10 Apart from these ill effects, exposure to these residues will in-directly give rise to antibioticresistant bacteria with antibiotic-resistant genes that can cause greater harm to humankind. 15,16 This will also cause current antibiotic therapy to treat various diseases in humans to become a failure and the World Health Organization (WHO) has also declared it a global threat. 17,18 Also, the prevalence of these residues in the environment will enable environmental microbiome selection pressure (through horizontal transfer of antibioticresistant genes among microbes), thereby resulting in the creation of an antibiotic-resistant gene reservoir thus contributing towards a global environmental antibiotic-resistance to pathogens. ...
Antibiotic residues in foods are a global threat and one of the main reasons for the antibiotic resistance development in bacteria as reported by WHO and many other agencies. Antibiotics...
... More specifically, Salmonella enterica serovar typhimurium shows acid tolerance to survive in simulated gastric fluid (SGF) through using its adaptive acid tolerance response (ATR) [23] and activating the PhoP-PhoQ (PhoPQ) two-component regulatory system makes Salmonella typhimurium resistant to bile salt [24]. For a long time, antibiotics have been commonly used to prevent disease outbreaks in shrimp farming [25], but the extensive and infrequent dose in shrimp culture might help develop antibiotic-resistant pathogens [26,27]. Significantly, the emergence of several antibiotic-resistant Salmonella serovars using shrimp as a vehicle causes significant morbidity and mortality in humans [28]. ...
Shrimp is the white gold of Bangladesh, with the second-highest income source from exporting to foreign countries. Contamination with Salmonella spp. is now one of the significant issues for Bangladesh to export. Proper characterization of the salmonella pathogen is thus necessary to avoid undesirable losses due to the rejection of exported shrimp. In Bangladesh, the present condition of raw shrimp contamination with pathogenic Salmonella serovars and their survival/virulence properties was not adequately characterized. In this study, we collected 43 raw shrimps as samples from different farms in Jashore, Khulna, and Sathkhira regions. We then maintained standard cultural and biochemical protocols for isolating Salmonella strains, followed by the molecular identification of particular Salmonella serovars. The standard method for checking its credibility to form biofilm in 0–10% NaCl, tolerate acid/bile stress likewise in the gastrointestinal tract, and resist antimicrobial pressure was performed individually with the particular pathogenic strains. Our results successfully identified eleven Salmonella strains with three typhimurium serovars and three enteritidis serovars, which have biofilm-forming capability up to 4–8% NaCl, acid/bile habituation alike stomach/small intestine of humans, and resistance against necessary antibiotics generally used in treating human and poultry infection signifying the impending danger in the shrimp industry. While previous studies of Bangladesh successfully isolated Salmonella only presumptively, our research focused mainly on molecular characterization of the human Salmonella pathogen along with important survival and virulent attributes, such as biofilm formation, acid/bile tolerance, and antibiotic resistance of selected S. typhimurium and S. enteritidis strains. Further study with more sampling will be necessary to confer the transmission route of the pathogen from the natural reservoir to the shrimp industry.
... This bacterial group is adapting to the environment by acquiring resistance genes from other resistant bacteria through a horizontal transfer mechanism (Imperial and Ibana, 2016;Lerner et al., 2019;Van Reenen and Dicks, 2011). This phenomenon is heightened by several factors, such as the increasingly selective stresses induced by clinical medication on the lactobacilli that colonize the human gastrointestinal tract (Ma et al., 2017) and from the wide use of antibiotics in the food chain (Willis, 2000), where often lactobacilli are intentionally added as starters. It is important to avoid that food becomes a promoter of new ARs or also a vector of them (Founou et al., 2016;Wang et al., 2006;McDermott et al., 2002;Van Reenen and Dicks, 2011). ...
Lactobacilli are a ubiquitous bacteria, that includes many species commonly found as part of the human microbiota, take part in the natural food fermentation processes, are used as probiotics, and in the food sector as starter cultures or bio-protectors. Their wide use is dictated by a long history of safe employ, which has allowed them to be classified as GRAS (General Recognized As Safe) microorganisms by the US Food and Drug Administration (FDA) and QPS (Qualified Presumption of Safety) by the European Food Safety Authority (EFSA, 2007EFSA, 2007). Despite their classification as safe microorganisms, several studies show that some members of Lactobacillus genus can cause, especially in individuals with previous pathological conditions, problems such as bacteremia, endocarditis, and peritonitis. In other cases, the presence of virulence genes and antibiotic resistance, and its potential transfer to pathogenic microorganisms constitute a risk to be considered. Consequently, their safety status was sometimes questioned, and it is, therefore, essential to carry out appropriate assessments before their use for any purposes. The following review focuses on the state of the art of studies on genes that confer virulence factors, including antibiotic resistance, reported in the literature within the lactobacilli, defining their genetic basis and related functions.
... Variation exists in the use of antibiotics in aquaculture among countries, with 13 authorised antibiotics in China and 5 in the UK (Liu et al. 2017). Those substances can have direct toxic effects on biota, and, in the case of antibiotics, produce antibiotic-resistant pathogens (Willis 2000). Antibiotics are the most used drugs, but hormones, antifungal agents, growth promoters and sedatives, among others, are also used in industrial aquaculture (Bottoni et al. 2010). ...
In recent decades, we have witnessed a rapid increase in world aquaculture production, the so-called ‘blue
revolution’. So as to provide a holistic overview of the socio-ecological threats coupled with this increase, a literature
review has been conducted. The following seven major socio-ecological impacts were identified: (i) the damage and
destruction of natural environments, (ii) discharges; (iii) a risk to wild fish and shellfish populations, (iv) spatial conflicts,
(v) threats to food security, (vi) unfairness in the access to commons; and (vii) the unequal distribution of benefits. So as to
move forward from ‘blue revolution’ to a ‘blue evolution’ and attain sustainable aquaculture, the following tools have been
identified as instrumental for the transition process: technical, management, governance and legal aspects.
... The improper disposal of unused or expired medications through sinks, dust bins, toilets as recorded in the present study (Table 2) is unfriendly to the environment and may be associated with detrimental effects to the environment [13] and acquatic organisms [19], antimicrobial resistance [35] and detrimental effects to the community health through drinking water [36]. Moreover,this practice may also lead to contamination of vegetables, fruitts and fish which may contain medications in trace amounts. ...
Background
The community practice towards disposal of expired and unused medications in spite of its adverse impact have been widely neglected in many developing countries. The available guidelines in Tanzania focus on the disposal of expired medications and cosmetics in hospitals and community pharmacies only.
Aim
The aim of this study was to assess the disposal practice of expired and unused medications at household level in Mwanza city, north-western Tanzania.
Methodology
The household based cross-sectional study was conducted among 359 randomly selected household members. Semi-structured questionnaires were used for interview during data collection and while STATA® version 13 was used for analysis.
Results
Out 359 households visited, 252 (70.19%) had medications kept in their houses at the time of data collection. Among them, 10 (4.0%) households had kept medications at their houses because they were still continuing with treatment while 242 (96.0%) kept unused medications which were supposed to be discarded. The main reason for keeping unused or expired medications at home was uncompleted course of treatment (199 (82.20%) after feeling that they had recovered from illness. The main reason for discarding medications were recovering from illness (141(48.7%) and expiry (136 (46.9%). The major discarding practices for medications were disposing into domestic trashes (219 (75.5%) and pit latrines (45 (15.5%). Majority of respondents (273 (76%) were aware that improper disposal of expired medications are detrimental to human health and environment in general.
Conclusion
Improper disposal of unused and expired medications at household level was a common practice in the study area. Tailor-made interventions by the Food and Drugs Authority (FDA) and other national as well as local stake holders are urgently needed to address the situation.
... Oxytetracycline is widely used to treat bacterial infections in aquaculture farms, such as vibriosis and furunculosis [23,24]. In spite of that, many infected cases have been detected among fish, particularly common carp, and this is may be related to that, the an extensive use of antibiotics can cause the development of antibiotic-resistant pathogens which can infect both cultured animals as well as humans [25][26][27]. ...
Abstract
Aim: This study was carried out to investigate the occurrence of potentially pathogenic species of Vibrio in seven
types of fish sampled from fish farms located in different districts in Basra governorate, Iraq.
Methods and Results: A total of 153 live fishes was collected from fish farms during the period January-
May 2016. Bacteria were isolated using selective medium thiosulfate citrate bile sucrose salt agar. Presumptive
Vibrio colonies were identified using the VITEK 2 system and selected biochemical tests. In the present study V.
alginolyticus (24 of 60) was the predominant species, followed by V. cholerae (10 of 60), V. furnisii (10 of 60), V.
diazotrophicus (7 of 60), V. gazogenes (5 of 60) and V. costicola (4 of 60). The signs of vibriosis appeared in three
types of fish, including Cyprinus carpio, Coptodon zilli and Planiliza subviridius in spite of the using Oxytetracycline
in most fish farms.
Conclusion: The results of the present study demonstrated the presence of pathogenic Vibrio species nearly
in all fish farms. So the farm owners should be concerned about the presence of these pathogenic bacteria which
also contributes to human health risk and should adopt best management practices for responsible aquaculture to
ensure the quality of fish.
... Four growth promoters (zinc bacitracin, virginiamycin, tylosin phosphate and spiramycin ) and avoparcin was banned by EU in 1997. In 1998 the use of all antimicrobials for growth promotion was stopped by Danish Food Industry (Willis, 2000). In 2005, use of enrofloxacin in food animals was banned by Food and Drug Administration (FDA), USA due to the increased levels of fluoroquinolone-resistant Campylobcter sp (Huyghebaert et al., 2011). ...
... Important contributions are made to prevent and control infectious diseases, in the past mainly focussing on the use of antimicrobial agents or chemical additives [13]. However, the emerging antimicrobial resistance, the potential transfer of antimicrobial resistance genes to fish or human pathogens [14] and the possibility that antimicrobials can enter the human food chain [15], stress the need to develop reliable alternatives. These latter should ensure a healthy microbial environment in the larval rearing tanks and hence decrease disease and mortality [16]. ...
Severe economic losses due to diseases in marine larviculture may be linked to vibriosis. To better understand the pathogenesis of vibriosis and evaluate new ways to prevent and combat this important disease, there is a great need for reliable and reproducible experimental infection models. The present study aimed at developing a challenge model for vibriosis in Dover sole larvae and testing its applicability to study the effect of the probiotic treatment. For that purpose, larvae were challenged at 10 days post hatching with Vibrio anguillarum WT, V. anguillarum HI610 or V. harveyi WT. Following administration of V. anguillarum WT via immersion at 1 × 107 colony forming units/mL, a larval mortality of 50% was observed at 17 days post-inoculation. In a next step, the probiotic potential of 371 isolates retrieved from Dover sole was assessed by screening for their inhibitory effects against Vibrio spp. and absence of haemolytic activity. One remaining isolate (V. proteolyticus) and V. lentus, known for its protective characteristics in seabass larvae, were further tested in vivo by means of the pinpointed experimental infection model. Neither isolate provided via the water or feed proved to be protective for the Dover sole larvae against challenge with V. anguillarum WT. This developed challenge model constitutes a firm basis to expedite basic and applied research regarding the pathogenesis and treatment of vibriosis as well as for studying the impact of (a)biotic components on larval health.
... Oxytetracycline is widely used to treat bacterial infections in aquaculture farms, such as vibriosis and furunculosis [23,24]. In spite of that, many infected cases have been detected among fish, particularly common carp, and this is may be related to that, the an extensive use of antibiotics can cause the development of antibiotic-resistant pathogens which can infect both cultured animals as well as humans [25][26][27]. ...
Aim: This study was carried out to investigate the occurrence of potentially pathogenic species of Vibrio in seven types of fish sampled from fish farms located in different districts in Basra governorate, Iraq. Methods and Results: A total of 153 live fishes was collected from fish farms during the period January- May 2016. Bacteria were isolated using selective medium thiosulfate citrate bile sucrose salt agar. Presumptive Vibrio colonies were identified using the VITEK 2 system and selected biochemical tests. In the present study V. alginolyticus (24 of 60) was the predominant species, followed by V. cholerae (10 of 60), V. furnisii (10 of 60), V. diazotrophicus (7 of 60), V. gazogenes (5 of 60) and V. costicola (4 of 60). The signs of vibriosis appeared in three types of fish, including Cyprinus carpio, Coptodon zilli and Planiliza subviridis in spite of the using Oxytetracycline in most fish farms. Conclusion: The results of the present study demonstrated the presence of pathogenic Vibrio species nearly in all fish farms. So the farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of fish.
... Oxytetracycline is widely used to treat bacterial infections in aquaculture farms, such as vibriosis and furunculosis [23,24]. In spite of that, many infected cases have been detected among fish, particularly common carp, and this is may be related to that, the an extensive use of antibiotics can cause the development of antibiotic-resistant pathogens which can infect both cultured animals as well as humans [25][26][27]. ...
Aim: This study was carried out to investigate the occurrence of potentially pathogenic species of Vibrio in seven types of fish sampled from fish farms located in different districts in Basra governorate, Iraq. Methods and Results: A total of 153 live fishes was collected from fish farms during the period January- May 2016. Bacteria were isolated using selective medium thiosulfate citrate bile sucrose salt agar. Presumptive Vibrio colonies were identified using the VITEK 2 system and selected biochemical tests. In the present study V. alginolyticus (24 of 60) was the predominant species, followed by V. cholerae (10 of 60), V. furnisii (10 of 60), V. diazotrophicus (7 of 60), V. gazogenes (5 of 60) and V. costicola (4 of 60). The signs of vibriosis appeared in three types of fish, including Cyprinus carpio, Coptodon zilli and Planiliza subviridis in spite of the using Oxytetracycline in most fish farms. Conclusion: The results of the present study demonstrated the presence of pathogenic Vibrio species nearly in all fish farms. So the farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of fish.
... From this study, it was observed that multiple antibiotics resistant E. coli isolates were resistant to antibiotics commonly used in clinical medicine. There has been increasing concern of the possible development of resistance to antimicrobial agents in the Enterbacteriaceae, especially E. coli, as a result of the use of such agents in animal feed (13) . ...
Fifty-eight Escherichia coli isolates were recovered from contaminated water bodies including river, ponds, lakes and canals. Their antibiograms and plasmid profiles were studied. Seven antibiotic resistance profiles were obtained. Out of the 58 isolates, 41 (70.68 %) exhibited resistance to 3 or more drugs, only 17 (29.31 %) isolates showed resistance to 1 or 2 antibiotics. Plasmid content and profile studies showed that the 52 (89.65%) E. coli drug resistant isolates carried plasmids ranging from 12.0 kb to 1.5 kb in size. Plasmids of six size ranges were detected among the isolates with multi-drug resistance. The multidrug resistant isolates were found to possess multiple plasmids with large sizes ranging from 7.6 to12 kb. Very high resistance (100%) was detected against tetracycline while the least resistance was noticed with sulfamethoxazole-trimethoprim (3.44 %) and chloramphenicol (5.17 %) among the isolates. In conclusion, Dhaka City is the major resrvoir of drug resistant E. coli having a large content of plasmid DNA.
... Additionally, PPCPs include many antibiotic compounds, which have been found to endure traditional wastewater treatment procedures (Miao et al. 2004;Gros et al. 2007;Zorita et al. 2009;Chang et al. 2010;Gao et al. 2012). When these compounds are constantly applied at low doses to the environment, as in RW irrigation, it accelerates the global increase in antibacterial resistance (Willis 2000;Witte 2000;Schwartz et al. 2003;Kumar et al. 2005;Stine et al. 2007;Kemper 2008;Pignato et al. 2009;Barker-Reid et al. 2010;Knapp et al. 2010;LaPara et al. 2011;Jechalke et al. 2013). This, in turn, may alter the physiology of microbiotic ecosystems (Martinez 2009;Schauss et al. 2009), leading to the evolution of more drug-resistant pathogenic bacteria. ...
Agricultural crops have a long history of being irrigated with recycled wastewater (RW). However, its use on vegetable crops has been of concern due to the potential prevalence of microcontaminants, such as pharmaceuticals and personal care products (PPCPs) in the latter, which represents a possible health hazard to consumers. We investigated the uptake of three PPCPs (atenolol, diclofenac, and ofloxacin), at three different concentrations in irrigation water (0.5, 5, and 25 μg L−1) in relation to three varying volumetric soil moisture depletion levels of 14 % (−4.26 kPa), 10 % (−8.66 kPa), and 7 % (−18.37 kPa) by various vegetable crop species. Experiments were conducted in a split-split block completely randomized design. PPCPs were extracted using a developed method of accelerated solvent extraction and solid phase extraction and analyzed via liquid chromatography mass spectrometry (LCMS). Results indicate that all treated crops were capable of PPCP uptake at nanogram per gram concentrations independent of the applied soil moisture depletion levels and PPCP concentrations. Ofloxacin was the chemical with the highest uptake amounts, followed by atenolol and then diclofenac. Although the results were not statistically significant, higher concentrations of PPCPs were detected in plants maintained under higher soil moisture levels of 14 % (−4.26 kPa).
... Nowadays, it is documented that the extensive use of antibiotics in agricultural animal production contributes to the development of antibiotic-resistant pathogens and that these microbes can infect both humans and domesticated animals (Khachatourians, 1998;Wegener et al., 1999;Willis, 2000). Resistance to antibiotics has been reported among Gram-negative bacteria isolated from farmed catfish in Vietnam, where antibiotics are commonly used (Sarter et al., 2007) and in Aeromonas hydrophyla isolated from cultured tilapia (Son et al., 1997). ...
In this study, The effects of partial diet replacement (0% as a control , 2 and 5% ) with poly-β-hydroxybutyrate (PHB) on growth performance, host response and gut microbial community of Siberian sturgeon (Acipenser baerii, Brandt) juveniles were investigated. The experiment results showed that PHB did not affect on the growth performances of sturgeon juveniles but changed hindgut microbial community and highest bacterial diversity was observed at level of 2%. A decreased gut pH in PHB containing diets, increased mineral uptake in sturgeon muscle. PHB affected on the lipid metabolism and decreased lipid content in juveniles muscle. The effect of PHB on the hindgut histology was not tangible but high dose of PHB decreased fold height in the anterior midgut. 2% PHB improved the immunity response in juveniles but the lowest amount of IgM level was observed in 5% PHB. We also investigated the effects of feeding Artemia nauplii enriched with or without PHB and /or HUFA on growth performance and gut microbial community in sturgeon larvae. The results showed that feeding Artemia nauplii enriched with PHB and PHB+HUFA decreased growth performances and tolerance to environmental stresses in the larvae. PHB increased lipid content and changed the microbial community in the hindgut.
... It is important to note its impact on the treatment and therapeutic strategy of serious infections [6][7][8][9][10]. Food animals, including poultry are one of the most important sources of development of multi-drug resistant (MDR) bacteria because of continuous use of antibiotics as feed additives and growth promoting factors in a sub-therapeutic level [11][12][13]. This practice may lead to selection of a resistant population in the native microbiota of the animal and the local environment due to shedding through feces. ...
Aim: The present study was conducted to record the association of extended spectrum β-lactamases (ESBLs) producing enteric bacteria with diarrhea of poultry birds in Mizoram, India.
Materials and Methods: Fecal samples were collected from poultry birds with the history of diarrhea from different parts of Mizoram. Samples were processed for isolation and identification of Escherichia coli, Salmonella, and Klebsiella pneumoniae. All the isolates were subjected to antibiotic sensitivity assays. Phenotypically, ESBLs production ability was determined by double discs synergy test (DDST) method. ESBLs producing isolates were subjected to polymerase chain reaction (PCR) for detection of ESBLs genes. Plasmids were cured by acridine orange. Transfer of resistance from donor to recipient strains was done by in vitro horizontal method.
Results: A total of 134 enteric bacteria was isolated, of which 102 (76.12%), 21 (15.67%) and 11 (8.21%) were E. coli, Salmonella spp. and K. pneumoniae, respectively. By DDST 7 (5.22%) isolates (6 E. coli and 1 K. pneumoniae) were ESBLs producer. PCR analysis confirmed 5 (3.73%) (4 E. coli and 1 K. pneumoniae) isolates harboured blaCTX-M-1 gene and/or blaTEM gene. All the isolates were carrying plasmids ranging between 0.9 kb and ~30 kb. Of the 4 isolates positive for blaCTX-M-1 and/or blaTEM, 2 (1.84%) were confirmed for blaCTX-M-1 gene in their plasmid. No blaTEM gene was detected from plasmid. The resistance plasmid could not be transferred to the recipient by in vitro horizontal gene transfer method.
Conclusion: ESBLs producing enteric bacteria are circulating in poultry in North Eastern Region of India. As poultry is one of the most common food animals in this region, these organisms may enter in human population through them.
... On the other hand, the widespread usage of antibiotics without regarding the withdrawal time for treated animals can cause to antibiotic residues in the edible tissues (Cañada-Cañada et al., 2009;Quesada et al., 2013;Reig & Toldrá, 2008). It is associated with the occurrence of allergic hypersensitivity reactions and therapeutic ineffectiveness in humans, as well as the development of antibiotic-resistant pathogenic microorganisms in the environment (Alderman & Hastings, 1998;Willis, 2000). ...
This study aimed to investigate the occurrence of antibiotic residues in rainbow trout muscle samples (n = 74) obtained from Iranian trout farms. The levels of the antibiotics were determined by in-house validated HPLC methods. Oxytetracycline, tetracycline, enrofloxacin, ciprofloxacin, and florfenicol residues were detected in 6.76%, 37.8%, 31.1%, 10.8%, and 14.9% of the samples, respectively; while chlortetracycline was not detected. The detected range of concentrations for positive samples was 8.94–81.2 μg/kg for oxytetracycline, 7.99–98.4 μg/kg for tetracycline, 6.75–87.4 μg/kg for enrofloxacin, 5.83–11.5 μg/kg for ciprofloxacin, and 49.9–313.6 μg/kg for florfenicol. None of the samples exceeded the maximum residue levels (MRLs) established by the Institute of Standards and Industrial Research of Iran. The co-occurrence of antibiotics was detected in 40.5% of the analyzed samples. The frequency of co-occurrence of enrofloxacin-tetracycline was the highest (16.2%). Despite the fact that concentrations of the analyzed antibiotics in trout samples did not exceed the MRLs, their co-occurrence in such a level could be a serious public health problem.
... Studies on presence of antibiotic residues in hospital effluent and in other environmental slots have been conducted across the world [10][11][12] . But in India very few studies estimated antibiotic residues in hospital effluents and other environment samples 13,14 . Furthermore, concurrent studies on antibiotic prescription quantity in a hospital, antibiotic residue levels in its wastewater and resistant bacteria in the effluent of the same hospital are few 15,16 . ...
Large quantities of antibiotics are been used to humans and hospitals are the primary sites of administering antibiotics. Due to continuous release of these antibiotics from hospital effluents into the environment, the aim of this study was to determine the presence of antibiotic residues in hospital effluents from south Indian by High performance liquid chromatography (HPLC) method. The main aim is to determine the presence of antibiotics in the hospital effluent qualitatively by HPLC. A total of ten samples were collected from hospitals of government teaching, government super speciality, private teaching, private super speciality and local clinics for identifying the presence of antibiotic residues and the samples were named as RPA1 to RPA10 respectively. The qualitative analysis of hospital effluent samples for presence of antibiotic residues was carried by high performance liquid chromatography (HPLC) grade methanol and water technique (Hydrophilic chamber technique) for all the ten samples. The results showed that Ciprofloxacin, Enrofloxacin, Oxytetracycline, Trimethoprim and Ampicillin were present in all most all the samples except sample RPA 9. The results indicated that 90% of the samples contained residues of at least one of the investigated antimicrobials. It was concluded that various group of antibiotics were present in the samples collected from hospital effluents. The presence of antibiotics in environment may lead to potential emergence of resistant bacteria that should be watched carefully.
... For example, Odu and Okomuda, (2013) reported 79.6% prevalence of Escherichia coli in cabbage sold at Port Harcourt, Nigeria and speculated that the pathogens in the vegetables may have been a direct reflection of sanitary quality of the cultivation water, harvesting, transportation, storage, and processing of the plant produce. With the occurrence of these pathogenic E. coli 0157:H7 strain in the environment, the possibility of development of antibiotic resistance phynotype is most likely, especially due increase phenomenom of increasing incidence of antimicrobial resistance (AMR) bacteria in humans, animals and the environment that has continue to be a challenge to public health, in both human and veterinary medicine, which needs increased monitoring, Willis, (2000). Uses of herbicides and insecticides have in recent years, increased the level and distribution of AMR phenotypes, Chang et al. (2013) and resistance genes. ...
This research investigated the pre-harvest prevalence of E. coli 0157:H7 on cabbage (Brassica oleracea var. capitata) grown with contaminated irrigations' water, of Sharada canal in Kano Nigeria and determined the level of antibiotic's susceptibility phenotype. E. coli 0157:H7 was isolated by enrichment on Tripticase Soy Broth (TSB), and transferred onto Sorbitol MacConkey agar plates, supplemented with 0.5% sodium thioglycolate, cefexime and potassium telurite (CT-SMAC) and Eosin Methlylene Blue (EMB) repetitively. Non Sorbitol fermented colonies were biochemically screened on Microbact 24E, Latex agglutination and tested on standard antibiotic. A total of 11(22.00%) E. coli 0157:H7 were observed with highest resistance of 54.55% on nalidixic acid, followed by gentimycin and ceporex with 36.36% each. A number of strains showed significant positive correlations, in susceptibility response to drugs like ceporex and streptomicin (r=0.624, P<0.05), pefloxacin and ofloxacin (r=0.624, P<0.05), gentimicin and pefloxacin (r=0.624, P<0.05), and cotrimothaxole and pefloxacin (r=0.624, P<0.05) respectively. Similarly eight patterns of multidrug resistance were observed, 27.27% of the isolates showed resistance of 2 to 5 antibiotics. The prevalence of E. coli 0157:H7 in cabbage coupled with the high multi-drugs resistance, is a subject of public health concerned and therefore call for active surveillance mechanism by government health agencies, for detection of possible E. coli 0157:H7 disease outbreak in the State in routine services.
... 58,59,60 Similar to the now widely discussed risks of wide-spread antibiotic use in other animal husbandry, the human health risks associated with antibiotic use in aquaculture ultimately stem from the fact that previously effective tools from the relatively limited set of antibacterial agents available in human medicine are rendered powerless when humans become infected by zoonotic pathogens or commensal bacteria that have been selected for resistance to antimicrobials through the continuous antimicrobial use in animal breeding, or when such animal pathogens transfer resistance, through the exchange of genetic material, to related, or even unrelated human pathogens. 61,62,63,64,65,66,67,68 The concern about loss of treatment effectiveness, even though not always getting the necessary attention, is critical. So much so, that numerous coalitions of experts and physicians have been formed to promote awareness of the threats of inappropriate use of antibiotics, and to push for changes in current decisions and practices regarding therapeutant application. ...
The growth and worldwide expansion of intensive aquaculture production over the past few decades has significantly increased the presence of aquaculture activities in estuarine and coastal waters, as well as the share of aquacultured products in the food supply. Negative experience with, and concern over the environmental impacts of intensive aquaculture practices, particularly those of shrimp and carnivorous finfish farming, and more recently of finfish ranching, has grown in parallel with industry expansion, leading, in turn, to an intensification in the debate over the appropriate substance, approach, and scope of industry regulation. The core of the debate over aquaculture regulation lies in the clash between a strong conviction among industry promoters that aquaculture is already over-regulated, and the reality of accumulating evidence that in spite of growing negative experiences with current intensive practices, relatively little has been learned and achieved in addressing various environmental implications of different types of aquaculture. A thorough and reflective understanding of the existing legal and regulatory system is a key factor in conducting and sustaining an informed and participatory discussion on the future of intensive aquaculture in the U.S., and on formulating societal expectations for industry environmental performance. This report aims to contribute towards the building and consolidation of such an understanding.
... It is important to note its impact on the treatment and therapeutic strategy of serious infections [6][7][8][9][10]. Food animals, including pigs are one of the most important sources of development of multi-drug resistant (MDR) bacteria because of continuous use of antibiotics as feed additives and growth promoting factors in a sub-therapeutic level [11][12][13]. This practice may lead to selection of a resistant population in the native microbiota of the animal and the local environment due to shedding through faeces. ...
Cephalosporins are major antimicrobials used to treat serious infections. However, their effectiveness is being compromised by the emergence of extended-spectrum β-lactamases (ESBLs). A total of 138 enteric bacteria were isolated from 53 faecal samples of pigs collected from different districts of Mizoram, of which 102 (73.91 %) were Escherichia coli, 26 (18.84 %) were Salmonella spp. and 10 (7.25 %) were Klebsiella pneumoniae. Phenotypic confirmatory test (Double Discs Synergy Test) showed that 8 (5.80 %) E. coli isolates were ESBLs producer. PCR analysis confirmed that out of the eight isolate, 7 (5.07 %) harboured bla
CTX-M-1
gene and/or bla
TEM
gene. Of the eight positive isolates, 7 (5.07 %) and 3 (2.17 %) were found to be positive for bla
CTX-M-1
gene and bla
TEM
gene, respectively, of which 3 (2.17 %) isolates were positive for both the genes. Only 4 (2.90 %) E. coli isolates carried bla
CTX-M-1
gene alone. Agarose gel electrophoresis showed that all the isolates were carrying plasmids ranging between 0.9 and ~30 kb. Out of the seven isolates positive for bla
CTX-M-1
and/or bla
TEM
, 2 (1.84 %) isolates were confirmed for bla
CTX-M-1
gene in their plasmid. Only one E. coli isolate was found to be positive for both the genes in its plasmid. The resistance plasmid could not be transferred to a recipient by in vitro horizontal gene transfer method.
... Resistance surveillance is well established as an essential cornerstone of any attempts to understand and control resistance [8][9][10][11][12][13][14] . An extensive literature survey was done on antimicrobial usage, antimicrobial resistance, challenges of antimicrobial resistance, strategies to minimize the spread of antimicrobial resistance, importance of antibiogram surveillance method. ...
Background Susceptibility of microorganisms to antibiotics is clearly decreasing in many Asian countries and is of particular concern in Streptococcus pneumoniae. The genetic relationship between penicillin-resistant S pneumoniae strains from across Asia suggests that resistant clones have spread within and between countries.
Purpose The study was designed to determine the susceptibility of respiratory microorganisms to antibiotics by using antibiogram reports.
Materials and methods The bacterial strains were isolated from patients suffering from respiratory tract infections (sputum, bronchial wash and throat swab, pleural fluids). Patients with respiratory tract infections having antibiogram were collected retrospectively and prospectively from the patient records and microbiology laboratory respectively. 147 subjects whose antibiogram reports available were included in the study.
Results The duration of stay in hospital varied among the population. In the retrospective study most of the patients (37.27%) were admitted for 6–10 days while 25.45% stayed for 1–5 days. In prospective study, most of the patients (37.83%) had a hospital stay of 6–10 days while 27.02% were admitted for 1–5 days. Due to increased resistance shown by previously susceptible organisms patients were at a risk of longer hospital stays. In retrospective phase, most of the patients received more than one antibiotic as part of the treatment. 34.54% patients were on two antibiotics while 25.45% were on three antibiotics. In the prospective study, the number of patients receiving only one antibiotic was high (43.24%), while 32.43% were on three antibiotics. The susceptibility of microorganisms was more evident in hospitals where the antibiotic usage is maximum. Hence pathogenic microorganisms can now defy antibiotics to which they were previously susceptible.
Conclusions The study emphasises that, antibiotic susceptibility testing should be carried out for all the patients who is in need of antibiotic therapy. Because of the immediate unavailability of antibiogram report it is better to obtain gram stain report before starting empirical therapy. Thereby it helps in choosing appropriate antibiotics having a narrow spectrum of activity. After obtaining the antibiogram report the sensitivity of the empirically started antibiotic should be checked against the same. Moreover the patient should be cautioned to follow the correct therapeutic regimen even after getting discharged from the hospital.
... and Xanthomonas spp. on several vegetable crops. Consequently, OTC residue may leave on or in these foods of plant origin contributing to emergence of resistant microorganisms (Willis, 2000). ...
Oxytetracycline (OTC) is used worldwide to protect crops against bacterial diseases. The US Environmental Protection Agency approved its use in apple, pear, nectarine, and peach, and set residue tolerance at 350 ng g−1. A europium-sensitised luminescence (ESL) method was developed for in-situ determination of OTC residue in these fruits. After extraction in Na2EDTA-NaCl-McIlvaine buffer at pH 4 and filtration, cleanup was performed using hydrophilic-lipophilic balance cartridges. ESL was measured using a portable time-resolved fluorometer. The signal responded linearly over three orders of magnitude (10–10000 ng g−1) with 17–50 ng g−1 limits of quantitation and 2% averaged relative standard deviation. Recoveries were 84% and 82% at 100 and 350 ng g−1, respectively. Inter-laboratory validation was performed by HPLC–MS/MS.Research highlights► Oxytetracycline (OTC) is quantified in-situ by europium-sensitised luminescence. ► A time-resolved analyser enables in-situ OTC quantitation for the first time. ► Sensitivity exceeds 350 ng g−1 tolerance in apple, pear, peach and nectarine. ► Liquid–liquid extraction is excluded saving both time and chemicals. ► Filtration replaces centrifugation to improve separation and deployability.
... Moreover, the use of pharmaceuticals is expected to increase following the completion of the human genome project and because of the increasing age of the population. One major concern is that antibiotics found in sewage effluent may cause increased resistance amongst natural bacterial populations and the increase in the number of bacterial strains resistant to multiple antibiotics has been attributed by several authors to the increase in discharges of antibiotics to waste-water (Willis, 2000). Guidelines for testing environmental impacts of new pharmaceuticals have been introduced in the US and a draft environmental risk assessment for new pharmaceuticals has been prepared for the EU. ...
on the environment and human health is a cause of increasing concern. Although many studies continue to be carried out on this subject, most address only individual chemicals or particular groups of chemicals, such as metals or radioactive substances. In this paper, we consider the availability of data and knowledge about potentially harmful chemicals from the national to international scale and suggest a strategy to help prevent chemical pollution or deficiencies damaging global sustainability into the 21st century. The main groups of chemicals considered are: (i) Potentially harmful inorganic elements such as As, Cd, Hg and Pb known to have adverse physiological effects at low levels, and elements and species such as Se, I and NO x that can be essential or harmful depending on their concentration, speciation and bioavailability. Chemical elements such as Ga, In and the PGEs that are increasingly used in the development of new materials, including nanotechnology applications, are also discussed briefly. (ii) Radioactive substances, including naturally occurring radioisotopes, such as 238 U and its decay products 226 Ra and 222 Rn, and processed materials, such as depleted uranium (DU), which affect the environment and human health because of their radiological and chemical toxicity. Data on isotopes from the nuclear industry, such as the relatively short-lived isotopes 137 Cs and 90 Sr, are also discussed, including from accidental releases such as Chernobyl in 1986. Isotopes with longer half-lives such as 243 Am and 240 Pu, which are important in the development of nuclear waste management strategies are also considered. (iii) Persistent organic pollutants (POPs) including many synthetic chemicals such as dichlorodiphenyltrichloro-ethane (DDT), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), flame retardants and their metabolites, which are char-acterised by their persistence, bioaccumulation (lipophilicity) and toxicity (PBT) properties. Other synthetic chemicals such as perfluorooctane sulphonate (PFOS), which have different bio-accumulation properties, are considered briefly. (iv) Human and veterinary pharmaceuticals, of which there is increasing evidence of their presence in the environment. These substances are of particular concern because many are designed to target specific biological receptors and hence can have potentially deleterious effects at exceptionally low concentrations. All these groups of chemicals include endocrine disrupting chemicals (EDCs), capable of disrupting animal and human hormone systems (including sex and thyroid). Geochemical databases such as those prepared by the Forum of European Geological Surveys (FOREGS) and the British Geological Survey (BGS) provide systematic information on levels of inorganic chemicals in the environment. Similarly, airborne radiometric databases provide systematic information on the distribution of radioactive substances. Examples of such data are used to demonstrate how the distribution of chemicals in the environment can be mapped, and how modelling and monitoring systems derived from them are of strategic importance in understanding the impact of chemicals on ecosystems and human health from the national to global scale. There is concern, however, about the lack of such systematic data for organic chemicals. It is argued that such systematic data for all chemicals is crucial for sustaining the Earth's life-support systems into the 21st century. © 2005 Institute of Materials, Minerals and Mining and Australasian Institute of Mining and Metallurgy. Published by Maney on behalf of the Institutes. Manuscript received 21 July 2004; accepted in final form 6 July 2005.
... It is widely recognized that the extensive use of antibiotics in agricultural animal production contributes to the development of antibiotic-resistant pathogens and that these microbes can infect both humans and domesticated animals (Khachatourians, 1998; American Academy of Microbiology, 1999;Wegener et al., 1999;Willis, 2000). Given the knowledge of resistance development it is possible that similar problems may exist in connection with the use of antibiotics in shrimp farming. ...
Summary The use of antibiotics in aquaculture may cause development of antibiotic resistance among pathogens infecting cultured animals and humans. However, this is a recent issue and has not yet been thoroughly investigated. Furthermore, there is limited knowledge about the environmental effects of antibiotic use in aquaculture. It is well known that antibiotics are commonly used in shrimp farming to prevent or treat disease outbreaks, but there is little published documentation on details of usage patterns. This study, conducted in 2000, shows that a large proportion of shrimp farmers along the Thai coast used antibiotics in their farms. Of the seventy-six farmers interviewed, 74% used antibiotics in shrimp pond management. Most farmers used them prophylactically, some on a daily basis, and at least thirteen different antibiotics were used. Many farmers were not well informed about efficient and safe application practices. A more restrictive use of antibiotics could have positive effects for the individual farmer and, simultaneously, decrease impacts on regional human medicine and adjacent coastal ecosystems. It is likely that dissemination of information could contribute to a decreased use of antibiotics, without decreasing the level of shrimp production.
... Antibiotics are normally used to prevent or treat disease outbreaks in shrimp farming [3]. However, extensive use of antibiotics in shrimp farming can cause the development of antibiotic-resistant pathogens which can infect both cultured animals as well as humans [4, 5]. Shrimp intended for export have to meet the bacteriological standards of the importing countries. ...
Salmonella and Vibrio species were isolated and identified from Litopenaeus vannamei cultured in shrimp farms. Shrimp samples showed occurrence of 3.3% of Salmonella and 48.3% of Vibrio. The isolates were also screened for antibiotic resistance to oxolinic acid, sulphonamides, tetracycline, sulfamethoxazole/trimethoprim, norfloxacin, ampicillin, doxycycline hydrochloride, erythromycin, chloramphenicol, and nitrofurantoin. Salmonella enterica serovar Corvallis isolated from shrimp showed individual and multiple antibiotic resistance patterns. Five Vibrio species having individual and multiple antibiotic resistance were also identified. They were Vibrio cholerae (18.3%), V. mimicus (16.7%), V. parahaemolyticus (10%), V. vulnificus (6.7%), and V. alginolyticus (1.7%). Farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of shrimp.
A residue of a parent drug or chemical and its metabolites may accumulate and be deposited or stored within the plant or animal (meat) tissues and organs following: the use of drugs or chemicals to control diseases; the use of drugs or chemicals to treat diseases; the use of feed additives to promote growth and improve feed efficiency.
The transcriptome and antibiotic resistance of Vibrio parahaemolyticus isolated from Penaeus vannamei cultured in seawater (strain HN1)and freshwater (strain SH1) ponds were studied at different salinity (2‰ and 20‰). At different salinity, 623 differentially expressed genes (DEGs) significantly upregulated and 1,559 DEGs significantly downregulated in SH1. In HN1, 466 DEGs significantly upregulated and 1,930 DEGs significantly downregulated, indicating high salinity can lead to the downregulation of most genes. In KEGG analysis, the expression of DEGs annotated to starch and sucrose metabolism pathway was higher at 2‰ salinity than at 20‰ salinity in HN1 and SH1, implying salinity affected bacterial growth mainly through this pathway. In the enrichment analysis of upregulated DEGs, two pathways (Valine, leucine, and isoleucine degradation, and Butanoate metabolism) were significantly enriched at different salinity. Antibiotic-susceptibility test discovered that SH1 isolated from P. vannamei cultured in freshwater was resistant to multiple drugs, including kanamycin, gentamicin, medemycin, and azithromycin, at a salinity of 2‰, whereas at 20‰ salinity, SH1 was not resistant to the drugs. The HN1 strain isolated from P. vannamei cultured in mariculture was resistant to polymyxin B and clindamycin at 20‰ salinity. Whereas, HN1 was intermediately susceptible to these two antibiotics at 2‰ salinity. These results indicate that the drug resistance of bacteria was affected by salinity. Furthermore, beta-lactam resistance was significantly enriched in SH1 at different salinity, and the inhibition zone of penicillin G was consistent with the results of a beta-lactam resistance pathway.
عزل وتشخیص البكتریا المرافقة لبعض الاصابات
المرضیة في بعض الاسماك في محافظة البصرة، العراق
Residues of antibiotics used in food-producing animals can be excreted in milk, affecting the technological performance of starter lactic acid bacteria (SLAB). SLAB development and acidification performance was studied in thermised ovine milk spiked with oxytetracycline (OTC) at maximum residue limit (MRL, 100 μg kg-1), during the early acidification phase. Late milk acidification and lower lactic acid concentration revealed an antibiotic effect mainly after 6 and 7 h from inoculation, with a 6 h delay to reach pH 5.6; the delay in SLAB development was observed by BactoScan™, while viable counts were not affected. Real-time PCR evidenced OTC effect for Streptococcus thermophilus and Lactobacillus helveticus, not for Lactobacillus delbrueckii subsp. lactis. A statistically significant impact of the antibiotic was observed, even at the maximum residue limit, with possible repercussions in technological processing and in human health, due to an increase of its concentration in cheese.
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Poultry products are some of the most important sources of protein in the world. Even though poultry is considered a healthy meat type, there are wide concerns regarding chemical contamination in poultry products. This review will describe some potential chemical contaminants in poultry meat and eggs. It also briefly discusses the regulatory process used in the US for the control of these contaminants as an example of prevention and control strategies used around the world.
Residual Level of antibiotics viz: Chloramphenicol, Sulphonamide, Tetracycline, Erythromycin, Streptomycin and β-Lactams were determined in farmed shrimps collected from major fish farms of Kerala, Tamil Nadu, Karnataka and Andhra Pradesh. Streptomycin, Tetracycline and β-Lactams could not be detected in any of the samples. Chloramphenicol, if at all present was found to be at trace level <1 ppb. Sulfonamides and Erythromycin were detected in farmed shrimps at a level < 100 ppb. Charm II assay was used to quantify the antibiotics in shrimps based on a binding reaction between the antibiotic molecules and antibody attached to microbial cell. Scintillation fluids added to the tube and the radio signals from 1H 3 or 6C 14 counted by Charm II system are recorded.
The goal of this study was to isolate commensal Escherichia coli from faeces of apparently healthy cattle and determine their susceptibility to commonly used antibiotics. Non-repeat faecal samples were collected from 320 ready to be slaughtered cattle and 1,051 commensal isolates of Escherichia coli were recovered from 240 of the faecal samples collected using standard bacteriological methods. All the bacterial isolates were first examined for their susceptibility to antibiotics using protocols as specified by the Clinical Laboratory Standards Institute. The frequency of the antibiotic resistance among the isolates is as follows: ampicillin, 896 (85.3%); cotrimoxazole, 134 (12.8%); gentamicin, 926 (88.1%); nahdixic acid, 98 (9.32%); mtrofurantom, 421 (40.1%); colistin, 662 (63.0%); streptomycin, 710 (67.6%) and tetracycline, 676 (64.3%). About 500 isolates were selected based on their antibiotic resistance phenotypes to determine their susceptibility to cephalosporins and flouroquinolones. The susceptibility of the isolates to cephalosporins are ceftazidime, 298 (59.6%); cefoxitin, 463 (92.6%); ceftriaxone, 107 (21.4%) and aztreonam, 241 (48.2%). The susceptibility to the flouroquinolones are: norfloxacin, 39 (7.8%); levofloxacin, 23 (4.6%); pefloxacin, 99 (4.6%); ofloxacin, 26 (5.2%) andciprofloxacin, 55 (11.0%). The study has confirmed that,5. coli recovered from cattle show high prevalence of antibiotic resistance.
This article establishes the estimate's mathematics model of the soybean's yield, using the artificial nerve network's knowledge, and by the model we can increase accuracy of the Soybean Yield Forecast. (The Journal of American Science. 2006;2(3):85-89).
Objective: To evaluate the effect of inorganic minerals and probiotics on pig performance and antimicrobial resistance. Materials and methods: Ninety-six crossbred pigs 17 to 20 days old were randomly assigned to six experimental diets. A non-medicated basal diet was supplemented with carbadox (55.12 g per tonne), copper sulfate (192.40 g copper per tonne), zinc oxide (2712.68 g zinc per tonne), or the probiotic feed additive BioPlus2B (Chr Hansen Inc, Milwaukee, Wisconsin; 1.1 × 106 or 1.3 × 106 spores per gram of feed). Pigs were weighed weekly and feed consumption was monitored to assess performance. Rectal swabs were collected for isolation of enterococci to evaluate antimicrobial resistance. Isolates were screened for resistance to vancomycin, and the broth microdilution procedure was used to determine minimum inhibitory concentration breakpoints. Results: The zinc oxide diet promoted the heaviest bodyweights and greatest feed consumption (P < .05). Feed:gain was similar for pigs fed the diets supplemented with carbadox, BioPlus2B at 1.3 × 106 spores per gram, copper sulfate, and zinc oxide. Enterococcal isolates were highly susceptible to vancomycin at the start and end of the study. Implications: Zinc oxide may sustain acceptable pig performance as the sole growth promotant in nursery diets. BioPlus2B in nursery pig diets did not enhance growth or feed utilization. In this study, the young pig did not represent a significant reservoir of vancomycin-resistant enterococci.
The factors influenced on the oasis ecosystem stability involve many aspects and the relationships among factors have the characteristic of uncertain and hierarchal. This paper takes the irrigation area of the north of Ningxia (that draws water from the Yellow River) as an example to compare the oasis ecosystem stability of ten calculated units with the method of fuzzy-hierarchal integrated evaluation. The results show that this method is scientific and rational, and is also an effective method to evaluate the oasis ecosystem stability. (The Journal of American Science. 2006;2(3):41-47).
The real-time polymerase chain reaction (RT-PCR), also called quantitative real-time polymerase chain reaction (QRT-PCR) or kinetic polymerase chain reaction (kPCR), is a technique used to simultaneously quantify and amplify a DNA molecule. It is used to determine whether a specific DNA sequence is present in the sample; and if it is present, the number of copies in the sample. It is the real-time version of quantitative polymerase chain reaction (qPCR), itself a modification of polymerase chain reaction (PCR). The procedure of RT-PCR follows the regular PCR procedure, but the DNA is quantified after each round of amplification. Two common methods of quantification are the use of fluorescent dyes that intercalate with double-strand DNA, and modified DNA oligonucleotide probes that fluoresce when hybridized with a complementary DNA. RT-PCR could be combined with reverse transcription polymerase chain reaction to quantify messenger RNA (mRNA) at a particular time for in a particular cell or tissue type. (The Journal of American Science. 2006;2(3):1-15).
The current focus on the development of sustainable urban drainage systems (SUDS) in many countries has raised awareness of the advantages of integrating constructed wetlands into urban and highway runoff treatment systems. However, it is essential that the criteria for the selection and design of constructed wetlands are rigorously applied to maximize their pollution treatment performance, and maintain and enhance their status as a valuable treatment option. A successful design of constructed wetlands for urban surface runoff management requires the adoption of an integrated multidisciplinary approach as performance criteria are difficult to set, given the inherent random fluctuations in discharge and pollution loadings that characterize storm water runoff. This temporal and spatial variability makes it difficult to define retention time and hydraulic loading, and thus general design rules for urban storm water wetlands have been developed from empirical performance data, using “single-number” techniques, such as drainage area ratio.
The chapter describes the management strategies undertaken by the NSW Department of Public Works & Services (DPWS) in utilizing wetland ecosystems integrated into the general landscaping/ streetscape design for the control/treatment of urban storm water. The management of urban storm water for water quantity and quality control/improvement are now becoming standard considerations in urban design. The drive toward urban consolidation emphasizes the development of innovative storm water management solutions.
"Survival of the fittest " holds good for men and animals as also for bacteria. A majority of bacteria in nature are nonpathogenic, a large number of them, live as commensals on our body leading a symbiotic existence. A limited population of bacteria which has became pathogenic was also sensitive to antibiotics to begin with. It is the man made antibiotic pressure, which has led to the emergence and spread of resistant genes amongst bacteria. Despite the availability of a large arsenal of antibiotics, the ability of bacteria to become resistant to antibacterial agents is amazing. This is more evident in the hospital settings where the antibiotic usage is maximum. The use of antibiotics is widespread in clinical medicine, agriculture, aquaculture, veterinary practice, poultry and even in household products. The major reason for this is the inappropriate use of antibiotics due to a lack of uniform policy and disregard to hospital infection control practices. The antibiotic cover provided by newer antibio
In this study, we investigated the effect of N-acyl homoserine lactone-degrading bacterial enrichment cultures (ECs) on larviculture of the giant freshwater prawn Macrobrachium rosenbergii.
The larval performance in terms of larval growth, larval survival, larval quality, duration of the larval rearing process and microflora levels in the rearing water as well as inside the prawn gut was investigated. The application of the EC bacteria was performed in two ways: by adding them directly into the larval rearing water and via enriched Artemia nauplii used for larval feeding. The results of the study demonstrated that both ECs that were tested had a similar positive effect on larval survival and larval quality, whereas they did not affect larval growth or the duration of the larval rearing process.
Under normal hatchery conditions, the optimal EC densities were found to be 10(6) CFU ml(-1) for adding into the rearing water and 5 × 10(8) CFU ml(-1) for enrichment of Artemia nauplii used for feeding of the larvae. In the hatchery, the ECs can be grown on waste streams of Artemia hatching.
Application of this kind of ECs could lead to a more sustainable aquaculture production, by replacing the use of antibiotics to control diseases.
In this study, the in vitro susceptibility of 209 campylobacter strains to the quinolones nalidixic acid, flumequine, ciprofloxacin, enrofloxacin, and to ampicillin, tetracycline and erythromycin was tested by the disk diffusion method. The strains were isolated from poultry abattoir effluent (DWA) and two sewage purification plants (SPA and SPB). Sewage purification plant SPA received mixed sewage, including that from a poultry abattoir, whereas SPB did not receive sewage from any meat-processing industry. The quinolone resistance of the DWA isolates ranged from 28% for enrofloxacin to 50% for nalidixic acid. The strains isolated from the sewage purification plants were more susceptible to the quinolones with a range of 11-18% quinolone resistance for SPB isolates to 17-33% quinolone resistance for SPA isolates. The susceptibility criteria as recommended by National Committee Clinical Laboratory Standards (USA) cannot readily be employed for campylobacter isolates. This investigation shows that the resistance of campylobacter bacteria is highest in the plant receiving sewage from a poultry slaughterhouse. Monitoring of antibiotic resistance of aquatic Campylobacter spp. is important, as surface waters are recognized as possible sources of infection.
In a survey of vancomycin resistant Enterococcus faecium (VREF) in Danish meat products, VREF could be detected in 16% of 160 samples of broilers collected at slaughterhouses and in 15% of 26 samples of pork collected from the retail trade. VREF were isolated by enrichment for 24 h in nutrient broth supplemented with vancomycin (50 micrograms/ml) prior to plating on Slanetz and Bartley agar. Using direct plating on Slanetz and Bartley agar, VREF could be isolated from only 1.7% of 540 samples of broilers from slaughterhouses and 2.2% of 90 samples of broilers from retail outlets. VREF was not detected in 124 samples of pork and 128 samples of beef from retail outlets by the direct plating method. An additional enrichment step in nutrient broth supplemented with vancomycin enhanced the detection rate of VREF by approximately three times compared to the direct plating method when investigating the same 160 samples of broilers by the two methods. The implications and public health aspects of VREF in food is discussed.
There is widespread concern about the presence of antimicrobial drugs in milk. The presence of drug residues in milk may have public health implications. Milk samples (n = 25 to 65/country) were collected from bulk tanks and commercial vendors in Barbados, Costa Rica, and Jamaica between February 1996 and August 1997. Bulk tank samples were collected from high milk-producing regions of Jamaica and Costa Rica and from 26 dairy farms in Barbados. Milk pH, bacterial growth (total CFU/ml and the presence of Streptococcus agalactiae and Staphylococcus aureus), and the presence of antimicrobials were determined. Milk samples were tested by a microbial inhibition test (Delvotest-P, Gist-Brocades Food Ingredients, Inc.) to screen for antimicrobial drugs. All positives were retested for the presence of beta-lactam antibiotics after incubating with penicillinase and some positives were identified by high-pressure liquid chromatography-UV. Mean pH values ranged from 6.5 to 6.7. S. aureus was identified in bulk tank samples from Costa Rica (52%), Barbados (44%), and Jamaica (46%). S. agalactiae was identified in bulk tank samples from Costa Rica (28%), Barbados (8 and 16%), and Jamaica (18%). Antimicrobial residues were detected in some bulk tank samples from Barbados (8%) and Jamaica (10%) but not in samples from Costa Rica. All positives in milk from Jamaica and Barbados were determined to be beta-lactams. No residues were detected in pasteurized milk samples from Barbados or ultrahigh-temperature milk from Jamaica. The presence of beta-lactam residues in some of these samples suggests the appropriateness of testing milk prior to processing for consumption.
Samples of cooked and raw prawns intended for human consumption were collected by officers at Southampton Port Health Authority, and tested for the presence of antimicrobial agents. Antimicrobial activity was detected in 23 out of 98 cooked prawn samples but in none of the 20 raw samples collected. Samples that showed antimicrobial activity were analysed using high performance liquid chromatography and immunoassay, resulting in the presumptive identification of trimethoprim in 15 samples, and low levels of gentamicin in three samples. Prawns in which trimethoprim was putatively detected contained bacteria with significantly greater resistance to this antibiotic than samples in which no trimethoprim was found. This suggests that the presence of antibiotics in prawn samples may be correlated with increased resistance to these drugs in the associated microflora. There are currently no guidelines regarding acceptable levels of antibiotics in seafood products. These results indicate that the use of these drugs by prawn farmers may be widespread, and may be an issue that requires further attention in the future.
During a field study in South India in 1989, faecal specimens were collected from residents in villages and the town of Vellore in South India. Examination of the faecal specimens revealed that virtually the whole population carried commensal bacteria resistant to trimethoprim, ampicillin and chloramphenicol. Most specimens contained more than one type of bacterium resistant to each antibiotic. There was less resistance to nalidixic acid, with a higher proportion in the town (33%) than in the villages (13%)
Besides hospitals animal husbandry represents a large reservoir of transferable antibiotic resistance genes. Via food products resistant bacteria can easily reach humans. The current debate is above all concerning antibiotic use as growth promoters which can be gradually phased out by better animal performance.
Following 10 days medication with oxytetracycline, marine sediment was sampled beneath three selected cages (cages 1, 2 and 3) at a fish farm over a period of 18 mnd., in order to detect any change in the sediment oxytetracycline concentration, bacterial number and bacterial resistance towards the drug. The bulk of oxytetracycline disappeared during the first weeks, but it persisted in the sediment at lower concentrations for quite some time after the medication. Half-life (f) of oxytetracycline in the sediment was measured as: 125, 144 and 87 days under cages 1, 2 and 3, respectively. At the end of the medication, all three sediments had > 100% oxytetracycline-resistant bacteria. This value dropped to 20% after 72 days and stabilised at levels of between 10 and 50%. The change in bacterial numbers, described as total and plate counts, was due to seasonal variations rather than to the medication.
A prospective study was undertaken to determine whether feeding farm animals antibiotics in feed caused changes in the intestinal bacterial flora of farm dwellers and their neighbors. Chickens were fed tetracycline-supplemented feed (tet-feed), and, as expected, within one week their intestinal flora contained almost entirely tetracycline-resistant organisms. Increased numbers of resistant intestinal bacteria also appeared, but more slowly, in farm members, but not their neighbors. Within five and six months, 31.3 per cent of weekly fecal samples from farm dwellers contained greater than 80 per cent tetracycline-resistant bacteria as compared to 6.8 per cent of the samples from the neighbors (P less than 0.001). Seven of the 11 farm members, but only three of the 24 neighbors, had two or more fecal samples containing greater than 80 per cent tetracycline-resistant coliforms (P less than 0.01). These resistant bacteria contained transferable plasmids conferring multiple antibiotic resistances. Selective pressure by tet-feed for antibiotic-resistant bacteria in chickens extends to human beings in contact with chickens and the feed.
During a field study in South India in 1989, faecal specimens were collected from residents in villages and the town of Vellore in South India. Examination of the faecal specimens revealed that virtually the whole population carried commensal bacteria resistant to trimethoprim, ampicillin and chloramphenicol. Most specimens contained more than one type of bacterium resistant to each antibiotic. There was less resistance to nalidixic acid, with a higher proportion in the town (33%) than in the villages (13%). Although there was little cross-resistance of the ampicillin-resistant strains to later generation cephalosporins, 50% were resistant to the combination of amoxycillin and clavulanic acid. There was no significant cross-resistance of the nalidixic acid-resistant strains to fluorinated 4-quinolones, despite the free availability of ciprofloxacin and norfloxacin in the area. The probable reason for the high incidence of resistance to first generation antimicrobials is the extensive use of these agents, coupled with continuous exposure to large numbers of faecal micro-organisms.
Eight hundred and eighty-three strains of Campylobacter spp. isolated between 1982 and 1989 from human stools and poultry products were screened for quinolone resistance. In this period the prevalence of resistant strains isolated from poultry products increased from 0% to 14%. During the same period the prevalence in man increased from 0% to 11%. The emergence of quinolone resistance has implications for the identification of campylobacter up to species level: the susceptibility for nalidixic acid can no longer be used as a criterion for identification in the laboratory. The rapid emergence of resistant campylobacter may also have important implications for the treatment and prophylaxis of diarrhoeal disease. The increase of quinolone resistance coincides with the increasing use of fluoroquinolones in human and veterinary medicine. Extensive use of enrofloxacin in poultry and the almost exclusive transmission route of campylobacter from chicken to man, in The Netherlands, suggests that the resistance observed is mainly due to the use of enrofloxacin in the poultry industry.
The prevalence of Escherichia coli carrying resistance factors (R factors) was examined in meat-consuming individuals and in those not consuming meat (vegetarians and babies below the age of 6 months). Assuming that the transport of resistant E. coli from animals through meat and meat products to the human consumer is most important, with regard to the incidence of resistant E. coli in man, we expected a significant difference in the proportions of people with resistant E. coli between the two groups. However, the percentage with resistant E. coli was larger in the group of vegetarians and babies than in the group of meat-eating individuals.
Ampicillin in low concentrations (1.7 and 5 g t-1) was incorporated in the feed given to 1-d-old chicks for 2 weeks. This was sufficient to select, in the intestinal contents, resistant Escherichia coli strains for which the minimum inhibitory concentration of ampicillin was > 100 micrograms ml-1. Different clones of E. coli were identified by their biotype, pattern of resistance to antibacterial agents and plasmid profile (designated P-P types). The experiment was repeated twice and the average proportion of ampicillin-resistant P-P types among 72 isolates of E. coli from chicks given feed containing 0, 1.7 and 5 g ampicillin t-1 were 10%, 31% and 46% respectively.
Six strains each of Enterococcus faecium and E. faecalis were investigated with respect to their resistance to heat and sodium hypochlorite. All enterococci survived the temperatures and holding times specified by the Department of Health (DoH) for the disinfection of 'foul and used' or 'infected' linen (65 degrees C for 10 min or 71 degrees C for 3 min). In addition, three strains (one E. faecium and two E. faecalis) could withstand 150 ppm available chlorine for 5 min, the treatment suggested by the DoH for the disinfection of heat labile materials. Further, our results showed that four strains of E. faecium were able to survive the British Standard for heat disinfection of bedpans (80 degrees C for 1 min). The significance of these findings with particular reference to the potential for enterococci to survive and disseminate in the hospital environment is discussed.
The choice of antibacterial drugs for the treatment of bacterial diseases in farmed salmonids changed dramatically during the period 1980-1994. In terms of treatment doses, oxytetracycline chloride was the most frequently prescribed antibacterial drug during the periods 1980-1983 and 1985-1986. In 1984, prescriptions changed in favour of furazolidone and trimethoprim/ sulphadiazine (1:5). Oxolinic acid was introduced for use in farmed fish in Norway in 1987, and immediately became the drug of choice, comprising 36% and 50% of the prescribed treatment doses in 1987 and 1988, respectively. In 1989, flumequine was temporarily approved for use in farmed salmonids, and during the period 1989-1994 antibacterial drug therapy in farmed salmonids acquired the character of "mono-therapy' with the quinolones flumequine and oxolinic acid. This rapid change-over in the choice of drug may partly be explained by the development of bacterial drug resistance in farmed salmonids, both to oxytetracycline and trimethoprim/sulphadiazine. The prescribing of furazolidone declined to zero during the study period. The morbidity caused by bacterial infections was defined as the number of treatment doses of antibacterial drugs per kg biomass of farmed salmonids per year. It was estimated that during the period 1988-1995, an average of 39% (mean value) of farmed salmon received, in theory, an antibacterial cure once each year. In comparison, the corresponding figure for the period 1981-1988 was 60%. However, in 1993 this figure fell to 13%, and declined even further in 1994 to 2.3%. The practice of on-farm mixing of medicated feed, using prescribed raw materials (pure drug substances) or premix formulations, declined significantly during the period 1992-1994. This was due to the introduction, in 1992, of new regulations on the prescribing of drugs to farmed fish.
The aim of this study was to determine the baseline pattern of resistance to aminoglycosides in a medical intensive care unit and to evaluate the influence on resistance rates of the use of amikacin as first-line aminoglycoside. A prospective bacteriological surveillance study was done during a 3-month baseline period with all aminoglycosides freely available, followed by a 9-month study period with predominant amikacin use. All patients admitted for more than 24 hours who were colonized or infected were included. Susceptibility rates for all isolates during the baseline period were 69% for amikacin, 32% for gentamicin, 35% for tobramycin and 46% for netilmicin. During the amikacin study period susceptibility rates rose to 75%, 43%, 44% and 51%, respectively. The increase in susceptibility to gentamicin and tobramycin, considering all isolates, was statistically significant. There was also a significant increase in susceptibility to netilmicin for gram-negative bacteria. There was no significant change in susceptibility to amikacin. We conclude that the use of amikacin as a first-choice aminoglycoside in a medical intensive care unit is warranted because of the better susceptibility rates and does not lead to a rapid rise in amikacin resistance. The predominant use of amikacin may have a favorable influence on susceptibility to the other aminoglycosides. To answer the question of whether these conclusions will remain valid over a longer period of predominant amikacin use, follow-up surveillance studies are mandatory.
Several reports have documented the presence of vancomycin-resistant enterococci (VRE) in the stools of asymptomatic individuals from the community who have neither recently been in hospital nor received antibiotics. Such findings were contrary to the then existing perception of VRE as a strictly hospital-acquired infection of debilitated and immunocompromised patients on specialized units. Community-acquired infections with VRE are extremely rare but those that do occur may be conspicuous because of their serious nature, for example, endocarditis. If asymptomatic faecal carriage of VRE is present in the community, individuals admitted to hospital and subjected to the selective pressures of antibiotics on the normal gut flora, may act as the source of hospital outbreaks. VRE have also been found in sewage, from stools of healthy farm animals and animal products. Avoparcin, a glycopeptide showing cross-resistance to medically important glycopeptides, has been used in the European Community as a growth promoter in animal feeds. A possible link between the use of avoparcin, the selection of VRE, and humans becoming colonized via the food chain exists. To prove such a link is beset with many difficulties: it is necessary to explain the presence of VRE in the United States where avoparcin is not used, and the predominance of the VanA gene over the VanB gene. It is also proving difficult to show that animal and human strains are identical by means of molecular typing. To date, molecular typing of strains is only suggestive of a link, but epidemiological studies of farms that use avoparcin have shown a significant association with the presence of VRE in animal stools. As long ago as 1969, the Swann report declared that an antibiotic of medical importance should not be used as a growth promoter in animal feeds. The vasy array of antibiotics now being used in animal husbandry and fish-farming, and the cross-resistance of some antibiotics to their medically important counterparts is a real cause for concern. The emergence of multi-resistant enterococci causing human infections and the possibility of the transfer of the VanA gene from VRE to methicillin-resistant Staphylococcus aureus (MRSA) emphasizes the importance of this problem.
Medical substances (pharmaceuticals) are a group of substances that until recently have been exposed to the environment with very little attention. The reason why they may be interesting as environmental micropollutants, is that medical substances are developed with the intention of performing a biological effect. Especially antibiotics used as growth promoters, as feed additives in fish farms are anticipated to end up in the environment. Very little is known about the exposure routes of the medical substances to the environment. Only few investigations have reported findings of medical substances in other field samples than sediment or treated waste water samples. Several substances seem to be persistent in the environment. This paper outlines the different anticipated exposure routes to the environment, summarises the legislation on the subject and gives an outline of present knowledge of occurrence, fate and effect on both the aquatic and terrestrial environments of medical substances. Present knowledge does not reveal if regular therapeutic use may be the source of a substance carried by sewage effluent into the aquatic system, even though clofibrate, a lipid lowering agent, has been identified in ground and tap water samples from Berlin. Further research would be necessary to assess the environmental risk involved in exposing medical substances and metabolites to the environment.
Strains of salmonella that are resistant to antimicrobial agents have become a worldwide health problem. A distinct strain of Salmonella enterica serotype typhimurium, known as definitive type 104 (DT104), is resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline and has become a major cause of illness in humans and animals in Europe, especially the United Kingdom.
To characterize typhimurium DT104 infections in the United States, we analyzed data collected by local and state health departments and public health laboratories between 1979 and 1996 in national surveys of the antimicrobial-drug resistance of salmonella. Selected typhimurium isolates with the five-drug pattern of resistance were phage typed.
The prevalence of typhimurium isolates with the five-drug pattern of resistance increased from 0.6 percent in 1979-1980 to 34 percent in 1996. In 1994-1995, such isolates were identified in samples from 36 of the 46 surveillance sites (78 percent). Thirty-nine of 43 typhimurium isolates with the five-drug pattern of resistance identified in 1994-1995 and 1996 were phage type DT104 or a closely related phage type.
Multidrug-resistant typhimurium DT104 has become a widespread pathogen in the United States. More prudent use of antimicrobial agents in farm animals and more effective disease prevention on farms are necessary to reduce the dissemination of multidrug-resistant typhimurium DT104 and to slow the emergence of resistance to additional agents in this and other strains of salmonella.
Two hundred and seventy-seven Enterococcus isolates representing the predominating enterococcal flora of retailed chicken and pork were identified by phenotypical features, and by random amplified polymorphic DNA. The resistance to nine different antibiotics was determined. Enterococcus faecium was the most frequently occurring species in both Swedish and Danish chicken. Enterococcus faecalis and unidentified groups of Enterococcus dominated in pork. Seventy-three per cent of the Enterococcus isolates from Swedish chicken were resistant to one or more of the tested antibiotics. The corresponding values for Swedish pork, Danish chicken and Danish pork were 9%, 55% and 14%, respectively. Tetracycline resistance was most frequent in isolates from Danish pork and Swedish chicken, while erythromycin resistance was most frequent in Danish chicken. Strains with acquired vancomycin resistance, mainly Ent. faecium, were found only on Danish chicken, except for one isolate from Danish pork. All vancomycin-resistant isolates contained the vanA gene. Vancomycin resistance could be transferred to a vancomycin-sensitive Ent. faecium strain from four of nine tested donor strains.
Editorial by Dixon and p 611)The use of genetic modification in food production is proving contentious and attracting much media coverage. Despite this, it can be difficult for anyone not directly involved to know how to obtain hard facts. Genetically modified foods raise many issues—scientific, technological, environmental, social, ethical, economic, and political—too many to cover here. This article therefore paints a broad picture of genetically modified foods and provides a lead to sources of information by addressing three specific points:What is genetic modification and how does it relate to food production?What are the current and future applications?What concerns do genetically modified foods raise?
Manipulating DNA
Genes change every day by natural mutation and recombination, creating new biological variations. Humans have been exploiting this for centuries—shuffling genes in increasingly systematic ways and using extensive crossing and artificial selection—to create many combinations that would never otherwise have occurred. Just about everything we eat is derived from livestock, crops, and micro-organisms bred specifically to provide food. Humans have also redistributed genes geographically: the soybean is native to Asia but is now grown throughout the Americas, and the potato, native to the American continent, is grown throughout the temperate world. DNA has never been “static,” neither naturally nor at the hand of people.
Genetic modification is an extension of this. However, unlike conventional breeding, in which new assortments of genes are created more or less at random, it allows specific genes to be identified, isolated, copied, and introduced into other organisms in much more direct and controlled ways (see boxes). The most obvious difference from conventional breeding is that genetic modification allows us to transfer genes between species. For example, the gene for bovine chymosin has been transferred to industrial micro-organisms—Kluyveromyces lactis (a yeast), Aspergillus niger var awamori (a fungus), and Escherichia coli K12 (a bacterium). These microbes are grown in fermenters to produce chymosin (rennet) on a commercial scale; this rennet, which replaces the conventional form obtained from slaughtered animals, is now widely used in cheese production.1
Predicted developments
A wide range of crops resistant to pests, diseases, and herbicidesFood materials with improved keeping and processing qualities (such as fruit much less susceptible to mould spoilage) and reduced or eliminated natural toxicants (such as glycoalkaloids in potatoes) or allergens (such as allergenic proteins in nuts)Better understanding of responses of crops to environmental stress and development of varieties that can grow in areas currently too inhospitableProduction of high value drugs such as vaccines in high volume agricultural crops such as oilseed rape or livestock such as in milk of dairy cattleDevelopment of renewable and sustainable sources of new materials (such as plastics based on starch or vegetable oil) in designer agricultural crops such as oilseed rape, potato, and maize
Box 1 : Manipulation of DNA
Genetic modification is possible only because the genes of all organisms are made of the same chemical—DNA. This means that DNA from two different organisms can be cut and joined together. Restriction enzymes cut DNA at specific sequences to create “sticky ends,” which, by virtue of their complementary base sequences, will tend to stick to other ends generated by the same enzyme. DNA ligase is used to re-join the DNA backbone when sticky ends pair up (fig 1).Plasmids, short loops of DNA found naturally in bacteria, are used to genetically modify bacteria. The plasmid is cut open with a restriction enzyme and mixed with the target gene, which has been similarly cut. DNA ligase is used to stitch the gene of interest into the plasmid. This “recombinant” plasmid is then mixed with bacteria, which, under appropriate conditions, take it up. The bacterial cells are genetically modified and can be cultured,isolated, subcultured, and, if appropriate, grown in fermenters on an industrial scale (such as in chymosin production). During culturing, the plasmid is replicated at each cycle of cell division,so that the final bacterial culture contains many copies of the plasmid and its inserted gene.To genetically modify plants or animals, the plasmid is extracted from the bacteria, and the cloned gene is excised with a restriction enzyme. The gene can then be introduced into individual plant and animal cells. For animals, this is usually done by injection of many millions of copies of the gene into the nucleus of a fertilised egg: in about 1% of cases the cloned gene will integrate into the zygote's chromosomes and, on cell division, be passed on to each cell in the embryo.For plants, there are various ways of introducing the gene into cells. A common method is to link the gene to a plasmid of the bacterium Agrobacterium, a naturally occurring plant pathogen. When plant cells are exposed to and infected by a non-virulent strain of the bacterium, the plasmid transfers to the plant cells, and its DNA integrates with that of the host cells. Genes of interest can be spliced into this plasmid, which is then used as a vector to carry the genes into plant cells (fig 2). The cells are then cultured to produce a callus (an undifferentiated cell mass), which, when grown on appropriate culture media, produces roots and shoots and develops into a plant, each cell of which is derived from a single parent cell and so contains the inserted gene.
View larger version:In a new windowDownload as PowerPoint SlideFig 1
Genetic modification also allows individual genes to be specifically switched off, through the antisense approach (see box 2). For example, a tomato paste now commercially available (and clearly labelled as genetically modified) was produced with this technology. The gene that controls fruit softening was selectively underexpressed (that is, turned down) in tomatoes. This gene codes for the enzyme polygalacturonase, which digests the pectin that cements the fruit cells together and acts as a natural thickener in tomato pastes; as less polygalacturonase is produced, more of the natural thickener remains in the ripe fruit, reducing the amount of energy required to thicken the paste.1
View larger version:In a new windowDownload as PowerPoint SlideFig 2 Method of producing genetically modified plants using a bacterial vector
Ap plications of genetic modification
It is now possible to introduce foreign genes (transgenes) into crop plants and express these in specific tissues (such as roots or leaves) and not in others (such as seeds and fruits). This is likely to substantially improve crop protection—for example, against pests that attack only roots or leaves.2
Present uses
In the United Kingdom to date, four genetically modified food materials have gained full approval and are in commercial use: cheese produced with genetically modified chymosin, tomato paste from slow softening tomatoes, and genetically modified soya and maize. Many others have cleared parts of the UK approval system (for example, clearance for food safety but awaiting environmental clearance for agricultural scale production).2 These include oil from oilseed rape, starch and oil from maize, oil from cotton, chicory, a slow softening tomato intended to be eaten fresh, and riboflavin from a microbe. In addition, other products granted full approval have not been developed to full commercial scale—for example, genetically modified brewers' yeast and bakers' yeast. 1 3
Most applications are for crop plants, and the genetic modifications are for commercially important agronomic traits—mostly herbicide tolerance and insect resistance. These agronomic traits are determined by single genes and are therefore easiest to manipulate. In contrast, characteristics such as flavour, texture, and processing qualities tend to be determined by multiple genes and are much more difficult to manipulate.
Future uses
Despite the technical difficulty, substantial progress is now being made with genetically modifying the compositional and processing characteristics of food crops. For example, oilseed rape can now be modified to produce oils with wide ranging characteristics through selective modification of the length and degree of saturation of the fatty acids produced—fatty acids such as laurate, typical of tropical vegetable oils, can now be produced in temperate oilseed crops. Similarly, the balance of sugar and starch in potatoes, which affects the processing quality of potatoes for snack food production (too much sugar produces a dark, poor tasting product), can also now be modified on an experimental scale.
Box 2 : Marker genes, constructs, and antisense technology
The gene of interest (such as one to delay fruit ripening) is not transferred alone but as part of a “construct.” In addition to the gene of interest, the construct contains short sequences to indicate where the gene of interest starts and stops; a “promoter,” which switches the gene on; and, probably, a marker gene. Typically, this marker gene will confer resistance to an antibiotic (coding for an enzyme that inactivates the antibiotic). This means that all cells containing the construct will be resistant to the antibiotic and,unlike cells that do not have the gene of interest, will be selected for on a medium containing the antibiotic.Antisense technology allows genes to be selectively turned down (underexpressed) or switched off altogether (not expressed at all). In this approach the gene of interest is attached to the promoter, but in reverse. This means that when the gene is read (during gene expression) it is the antisense DNA strand that is read rather than the sense (or usual) strand. “Antisense genes” block the expression of “sense genes”; this might be because the sense and antisense RNAsgenerated during gene expression are complementary so that they associate as an inactive complex, although the mechanism is not fully understood.
Modern genetic techniques are being used to identify and manipulate the genes for biologically active components of food crops, such as natural toxicants (for example, potato glycoalkaloids and kidney bean lectin), antinutrients (for example, trypsin inhibitors), and allergens (for example, certain nut proteins).3 Such developments are at early stages but in the longer term are almost certain to lead to the development of foods that lack these undesirable components.
On an industrial scale, deterioration of fruits and vegetables is a huge problem: for example, the tendency of plant tissue to turn brown at a cut or peeled surface often has to be controlled through the use of preservatives such as sulphite. Damaged cells release the enzyme polyphenol oxidase, which catalyses the conversion of monophenols
(released from separate subcellular compartments) to quinones, which oxidise to form brown polyphenolic pigments. However, the gene for polyphenol oxidase has been switched off in experimental studies by genetic modification, blocking this discolouration spoilage.4 Genetic modification and other molecular and biochemical techniques are being used to completely unravel the biochemistry of fruit and vegetable ripening and deterioration, and many new methods of preserving these foods, without the use of chemical preservatives, are likely to be developed.
Another possibility generating much interest is the use of crops to provide renewable sources of valuable materials such as vaccines, drugs, bioplastics, and other industrial materials.5 In parallel, cattle and sheep are being genetically modified to produce pharmaceutical chemicals in their milk, so that drugs can be produced much more efficiently and cost effectively.6 Although full discussion of this is beyond the scope of this article, there is hope that food crops such as banana could be used to produce and deliver vaccines in tropical regions.7
Issues of concern
In his recent editorial on genetically modified foods Burke touched on the main consumer concerns,8 but it is worth looking further at two other closely related concerns: the safety of genetically modified foods and the use of marker genes that confer antibiotic resistance. Environmental concerns are also important9 but are beyond the scope of this article.
Safety
The United Kingdom has led the world in developing systems for assessing the safety of genetically modified foods. 10 11 Consequently, genetically modified foods are subject to a rigorous safety assessment, based on rational scientific evaluation by leading experts and, by definition, within the limits of current knowledge. 1 12
Within the European Union genetically modified foods are now regulated on a union-wide basis.13
The recently widely reported work on potatoes at the Rowett Institute shows how difficult it can be to identify the facts (reviewed by Coghlan and Kleiner14). Initial media reports claimed that the research proved that all genetically modified foods were inherently unsafe; subsequently it became clear that the findings related not to genetically modified potatoes at all but to potato material to which concanavalin A (a lectin and known toxin) had been added.14 This emphasises the need to identify concerns precisely and assess claims critically.
Another case often cited as showing that genetically modified foods are inherently dangerous is that of the US company Pioneer Hi-Bred, which introduced genes from Brazil nuts into soybeans to increase the level of sulphur-rich amino acids. The soya was intended for animal feed, not human food. During tests it became clear that the nut protein that was transferred to soybean was allergenic to humans, and the company elected not to pursue the development, citing the potential difficulties of preventing the soya from entering the human food chain.15 The point that is usually not emphasised in coverage of this case is that the problem was identified because safety checks were, and continue to be, in place to identify the unintended introduction of an allergen into a genetically modified crop. 10 15
Antibiotic resistance
The use of antibiotic resistance as a marker system for gene uptake (see box 2) rightly continues to generate much concern. Again, it is important to identify and deal with specific concerns and not to condemn a general approach which has been invaluable in making genetic modification technically feasible. In general, the antibiotics used in marker systems are not used for treating diseases, and the gene and its product (that is, the enzyme that inactivates the antibiotic and thus confers resistance) would usually be destroyed during heat processing of the food material. 1 16
However, in two cases clinically important antibiotics have been used: a maize developed by Novartis contained a gene for ampicillin resistance, and a potato developed by Avebe contained a gene for amikacin resistance. A further complication with the maize is that the material was intended to be used unprocessed in animal feed and that the antibiotic resistance gene was under the control of a bacterial promoter. This led to concerns that the antibiotic resistance gene might be transferred to animal gut flora (including human pathogens), which might then acquire resistance to a clinically useful antibiotic. As a consequence, both these genetically modified crops are having difficulties gaining full regulatory approval.17 The Advisory Committee on Novel Foods and Processes has called for the development of different marker systems,16 and there are signs that alternative technologies are being developed.1 In the meantime it is imperative that the clinical use of antibiotics is not compromised.
Conclusions
Genetically modified foods have arrived. Those already on supermarket shelves have been subjected to rigorous safety assessment, as will the many more currently under development. Where genetic modification has introduced substantial changes, consumers will be informed through statutory (and additional voluntary) labelling. 11 18
In the heat of the debate it is easy to forget that DNA is, and always has been, part of our daily diet. Daily, each of us consumes millions of copies of many thousands of genes. Many of these genes are fully viable at the point of consumption, and in most cases we do not know what they do.How many people stop to consider the viable yet unknown genes of tomato, cucumber, and lettuce in a salad, the bovine genes in a beef steak, the fragmented DNA in many processed foods, and the genes of the many micro-organisms that we breath and swallow?
We are right to take seriously the development of genetically modified foods, to debate the issues that their use raises, and to question critically the risks and benefits they present. At the same time, however, it is important to avoid hysteria, to define clearly the issues of concern, and to tackle these rationally and on an informed basis.
Acknowledgments
Competing interest: None declared. Campden and Chorleywood Food Research
Association is an independent, member based, not for profit association that provides scientific, technical, and information services to the food, drinks, and allied industries and government agencies.
References↵Border P, Norton M.Genetically modified foods—benefits and risks, regulation and public acceptance. London:Parliamentary Office of Science and Technology,1998.↵Jones L, Haine H.Modern biotechnology in food production. Bulletin No 1-5. Chipping Campden:Campden & Chorleywood Food Research Association,1997.↵Jones L.Food biotechnology: current developments and the need for awareness.Nutr Food Sci1996; 6:5–11.↵Bachem CWP, Speckmann GJ, van der Linde PCG, Verheggen FTM, Hunt MD, Steffens JC, et al.Antisense expression of polyphenol oxidase inhibits enzymatic browning in potato tubers.Biotechnology1994; 12:1101–1105.OpenUrlCrossRef↵Coghlan A.Grow your own vaccines.New Scientist1995 Jan 21:23.↵Henninghausen L.Transgenic factor VIII: the milky way and beyond.Nature Biotechnology1998; 15:945–946.OpenUrl↵Kiernan V.Yes, we have vaccinating bananas.New Scientist1996 Sep 21:6.↵Burke D.Why all the fuss about genetically modified foods?BMJ1998; 316:1845–1846.OpenUrlFREE Full Text↵Anderson A, ed. Living in a genetically modified world.New Scientist (special edition) 1998 Oct 31.↵Advisory Committee on Novel Foods and Processes.Guidelines on the assessment of novel food and processes. Advisory Committee on Novel Foods and Processes report on health and social subjects No 38. London:HMSO,1991.↵Burke D.What can biotechnology do for the food industry? 19th annual Campden day lecture. Chipping Campden:Campden & Chorleywood Food Research Association,1997.↵Rossiter L.Biotechnology factfile—a quick reference guide. Watford:Institute of Grocery Distribution,1997.↵The novel foods and novel food ingredients regulations 1997, statutory instrument No 1335. London:Stationery Office,1997 (EU regulation 258/97 on novel foods and novel food ingredients.)↵Coghlan A, Kleiner K.Spud U dislike.New Scientist1998 Aug 15:5.↵Allen AH.Biotechnology: regulations may help consumer acceptance.Food Product Design1996 May:80–5.↵Advisory Committee on Novel Foods and Processes.Report on the use of antibiotic resistance markers in genetically modified food organisms. London:ACNFP,1994.↵MacKenzie D.Modified potato is taken off the menu.New Scientist1998 Oct 17:13.↵Communication and labelling guidelines for genetically modified foods. Watford:Institute of Grocery Distribution,1997.
Editor—In Piddock’s editorial on fluoroquinolone resistance it was stated that Salmonella typhimurium with decreased susceptibility to fluoroquinolones and campylobacter resistant to fluoroquinolones have been isolated from animals and retail poultry.1 Unfortunately, information about the incidence of fluoroquinolone resistant S typhimurium and campylobacter from human infections was not provided, nor was there any reference to underlying epidemiological events leading to the development of resistance.
The Laboratory of Enteric Pathogens is the national reference centre for salmonellas from humans in England and Wales. Since 1990 the most common serotypes have been S enteritidis, S typhimurium, S virchow, and S hadar. These are primarily zoonotic in origin, and the main food animal reservoirs are poultry, cattle, and pigs. In 1996, 702 of 5849 (12%) isolates of S typhimurium were resistant to ciprofloxacin at 0.125 mg/l, a 12-fold increase since 1994.2 Of particular importance has been the increasing occurrence of ciprofloxacin resistance in phage type 104 (DT104) already resistant to ampicillin, chloramphenicol, streptomycin, sulphonamides, and tetracyclines, with 12% of DT104 resistant to ciprofloxacin in 1996 and 1997.3 This increase is subsequent to the licensing in 1993 of ciprofloxacin analogues for use in animal husbandry and is also reflected in food animals, with 78% of isolates of DT104 from turkeys, 31% from chickens, 11% from cattle, 5% from pigs, and 12% from sheep resistant to quinolones in 1997.4 Concern has been expressed about the therapeutic implications for humans of fluoroquinolone resistance in multiresistant DT104, and a lack of clinical response has recently been reported from Denmark in an outbreak of quinolone resistant DT104 associated with pork in which seven people were admitted to hospital—six were treated with fluoroquinolones and one died.5
The Laboratory of Enteric Pathogens is also the national reference centre for campylobacter species from humans, and of 5800 isolates referred in 1996 and 1997, 12% were resistant to ciprofloxacin at >8 mg/l, and a further 4% had a ciprofloxacin minimum inhibitory concentration of 0.5 mg/l. Ciprofloxacin resistance was most pronounced in Campylobacter coli, with 22% of isolates resistant.
The report from Denmark shows the clinical consequences for humans of the continuing use of fluoroquinolone antibiotics in food animals. A recent report by the House of Lords Select Committee on Science and Technology has recommended the rapid introduction of a code of practice on the use of fluoroquinolones in food animals. In light of the Danish experience, it is hoped that these recommendations will be rapidly implemented.
In Italy, 18 months after the ban of avoparcin, the percentage of poultry meat samples containing vanA gene-positive vancomycin-resistant enterococci fell from 14.6% to 8%.
This review article provides a general analysis of the legal challenges presented by antimicrobial use in food animal production and the emerging public health responses to such use. The article stresses the importance of national and international law to the public health strategies and the interdependence between national and international law. The article argues that antimicrobial use in food animal production poses a challenge to the development of global health jurisprudence. (C) Elsevier, Paris.
Chicks hatched and reared in the absence of bacteria and fungi grow 15 to 25% faster than conventional chicks on the same autoclaved casein-starch or soybean meal-corn diet. The increased growth rate is not due to improved feed efficiency but is related to the fact that the germ-free chicks eat more than the conventional chicks.
Better growth was obtained when potassium and calcium were provided in the diet in the form of potassium monophosphate and calcium carbonate rather than as calcium phosphate.
In repeated experiments over a two-year period using two different diets no growth response to dietary penicillin supplements was observed either in the germ-free or in the conventional chicks which were kept in an animal room where chicks had not been raised previously. A growth response to penicillin was obtained only after the animal room was deliberately “infected” with intestinal contents from chicks reared in premises where a growth response to antibiotics occurred regularly. The growth-promoting effect of dietary penicillin is shown to be due to a reversal of a transmissible growth-depression condition.