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Heavy Use of Prophylactic Antibiotics in Aquaculture: A Growing Problem for Human and Animal Health and for the Environment
Abstract
The accelerated growth of finfish aquaculture has resulted in a series of developments detrimental to the environment and human health. The latter is illustrated by the widespread and unrestricted use of prophylactic antibiotics in this industry, especially in developing countries, to forestall bacterial infections resulting from sanitary shortcomings in fish rearing. The use of a wide variety of antibiotics in large amounts, including non-biodegradable antibiotics useful in human medicine, ensures that they remain in the aquatic environment, exerting their selective pressure for long periods of time. This process has resulted in the emergence of antibiotic-resistant bacteria in aquaculture environments, in the increase of antibiotic resistance in fish pathogens, in the transfer of these resistance determinants to bacteria of land animals and to human pathogens, and in alterations of the bacterial flora both in sediments and in the water column. The use of large amounts of antibiotics that have to be mixed with fish food also creates problems for industrial health and increases the opportunities for the presence of residual antibiotics in fish meat and fish products. Thus, it appears that global efforts are needed to promote more judicious use of prophylactic antibiotics in aquaculture as accumulating evidence indicates that unrestricted use is detrimental to fish, terrestrial animals, and human health and the environment.
... The improved hematological variables of the herbs were similarly observed in other studies. In the study of Aly et al. (2010), the results showed a significant increase in Hct values, the total WBC and lymphocytes when fish diets were supplemented with garlic (Allium sativum) and echinacea (Echinacea purpurea) (Aly and Mohamed, 2010). Similarly, in the study of Acar et al. (2015), citrus (Citrus sinensis) essential oils added to the diet improved the hematological parameters of fish. ...
... The improved hematological variables of the herbs were similarly observed in other studies. In the study of Aly et al. (2010), the results showed a significant increase in Hct values, the total WBC and lymphocytes when fish diets were supplemented with garlic (Allium sativum) and echinacea (Echinacea purpurea) (Aly and Mohamed, 2010). Similarly, in the study of Acar et al. (2015), citrus (Citrus sinensis) essential oils added to the diet improved the hematological parameters of fish. ...
The study focused on investigating the effectiveness of essential oils of peppermint (Mentha piperita) against Streptococcus agalactiae (bacteria causing hemorrhagic disease) in red tilapia with an infective concentration of 10 6 CFU/mL. The experiment was arranged with 2 control treatments: control 1-commercial feed + no infection; control 2-commercial feed + infection of S. agalactiae; and 3 experimental treatments with essential oils concentrations of 0.125%; 0.25% and 0.5%. The study examined the blood cell morphology and physiological blood indices of red tilapia (including hemoglobin; hematocrit; red blood cells count; the total number of white blood cells and thrombocytes, erythrocyte size) at three stages: after 15 days of adding essential oils without infection; five days after infection; and ten days after infection. In this study, fish supplemented with peppermint essential oils stimulated the body to create immunity. However, concentrations of 0.125% and 0.25% showed higher results about this ability in the presence of bacteria while the concentration of 0.5% exhibited a higher antibacterial effect of essential oils.
... Several studies have suggested that the antimicrobial resistances found in bacteria associated with aquaculture can be transferred to human pathogenic bacteria (Kruse & Sørum, 1994;Rhodes et al., 2000). Zoonotic pathogens resistant to multiple antibiotics and carrying resistance genes have been isolated from aquaculture farms including water, sediment, shrimp or fish, farm workers, probiotics, feed, etc. (Miranda & Zemelman, 2001;Cabello, 2006;Grema et al., 2015;Chuah et al., 2016;Santos & Ramos, 2018). Similarities in ARGs between fish and human pathogenic bacteria have speculated the human health implications of antibiotic use and resistance development in aquaculture settings (Kim et al., 2004;Obayashi et al., 2020). ...
... In Nigerian fish farms where antibiotics such as chloramphenicol, tetracycline, and gentamicin are used, aquaculture-associated bacteria were highly resistant to these antibiotics (Olatoye & Afisu, 2013;Fakorede et al., 2020). The association of ARGs with highly transmissible genetic elements such as the plasmids or integrons has been reported in several zoonotic bacterial pathogens such as Aeromonas hydrophila, Vibrio cholerae, and Salmonella enterica (Cabello, 2006;Ishida et al., 2010;Defoirdt et al., 2011;Zhang et al., 2015). The use of antibiotics in Chilean salmon aquaculture resulted in antibiotic residues and the presence of resistant bacteria harboring ARGs in 8-km-distant marine sediments. ...
... Anthropogenic impact on natural environments, due to misuse of antibiotics for medical and agricultural purposes is mainly responsible for the origination and dissemination of antibiotic resistance in natural environments (Hawkey 2008;Cabello 2006;Chee-Sanford et al. 2001;Goni-Urriza et al. 2000). Bacteria harboring ARGs usually thrive in antibiotic dense habitats such as human and livestock gut, agricultural soil and antibiotic-resistant bacteria (ARB) resulting from atmospheric deposition and aquatic circulation. ...
... On the other hand, Miller et al. (2009) described the lower frequency of multiple antibiotic resistances among native Antarctic bacteria which increased with an increase in anthropogenic activities. Usually, it is believed that the effect of anthropogenic activities on pristine environments plays a vital evolutionary role in the origination of multiple AR bacteria Cabello 2006 11 (68.75%) 1 (6.25%) 3 (18.75%) 1 (6.25%) 16 tetA 4 (50%) 0 2 (25%) 2 (25%) ...
Natural pristine environments including cold habitats are thought to be the potent reservoirs of antibiotic-resistant genes and have been recurrently reported in polar glaciers’ native bacteria, nevertheless, their abundance among the non-polar glaciers’ inhabitant bacteria is mostly uncharted. Herein we evaluated antibiotic resistance profile, abundance of antibiotic-resistant genes plus class 1, 2, and 3 integron integrases in 65 culturable bacterial isolates retrieved from a non-polar glacier. The 16S rRNA gene sequencing analysis identified predominantly Gram-negative 43 (66.15%) and Gram-positive 22 (33.84%) isolates. Among the Gram-negative bacteria, Gammaproteobacteria were dominant (62.79%), followed by Betaproteobacteria (18.60%) and Alphaproteobacteria (9.30%), whereas Phyla Actinobacteria (50%) and Firmicutes (40.90%) were predominant among Gram-positive. The Kirby Bauer disc diffusion method evaluated significant antibiotic resistance among the isolates. PCR amplification revealed phylum Proteobacteria predominantly carrying 21 disparate antibiotic-resistant genes like; blaAmpC 6 (100%), blaVIM-1, blaSHV and blaDHA 5 (100%) each, blaOXA-1 1 (100%), blaCMY-4 4 (100%), followed by Actinobacteria 14, Firmicutes 13 and Bacteroidetes 11. Tested isolates were negative for blaKPC, qnrA, vanA, ermA, ermB, intl2, and intl3. Predominant Gram-negative isolates had higher MAR index values, compared to Gram-positive. Alignment of protein homology sequences of antibiotic-resistant genes with references revealed amino acid variations in blaNDM-1, blaOXA-1, blaSHV, mecA, aac(6)-Ib3, tetA, tetB, sul2, qnrB, gyrA, and intI1. Promising antibiotic-resistant bacteria, harbored with numerous antibiotic-resistant genes and class 1 integron integrase with some amino acid variations detected, accentuating the mandatory focus to evaluate the intricate transcriptome analysis of glaciated bacteria conferring antibiotic resistance.
Graphical abstract
... are sensitive to most antimicrobials of significance [6]. As many Vibrio species are zoonoses, antimicrobials in aquaculture settings are used to not only control such bacterial infections but also to facilitate growth promotion in reared seafood species [7]. However, the excessive use of antimicrobials in aquaculture and human settings has led to the rapid emergence and evolution of antimicrobial resistance (AMR) in Vibrio spp. ...
... However, the excessive use of antimicrobials in aquaculture and human settings has led to the rapid emergence and evolution of antimicrobial resistance (AMR) in Vibrio spp. over the last few decades [7,8]. AMR develops when the bacteria is able to adapt and grow even in the presence of bacteriostatic or bactericidal antimicrobials, resulting in the loss of effectiveness of the drug [9]. ...
Vibrio parahaemolyticus is a causative pathogen for gastroenteritis involving the consumption of undercooked or raw seafood. However, there is a paucity of data regarding the quantitative detection of this pathogen in finfish, while no study reported the enumeration of haemolytic antimicrobial-resistant (AMR) V. parahaemolyticus. In this study, ampicillin-, penicillin G- and tetracycline-resistant and non-AMR haemolytic V. parahaemolyticus isolates were monitored and quantified in grey mullet samples reared locally from different premises within the food chain (farm and retail). Occurrence data for haemolytic V. parahaemolyticus were 13/45 (29%) in farm fish samples, 2/6 (one third) from farm water samples and 27/45 (60%) from retail fish samples. Microbial loads for haemolytic V. parahaemolyticus microbial loads ranged from 1.9 to 4.1 Log CFU/g in fish samples and 2.0 to 3.0 Log CFU/g in farm water samples. AMR risk assessments (ARRAs) for both the full farm-to-home and partial retail-to-home chains in the risk modelling framework were conducted, specifically for ampicillin, penicillin G, tetracycline and haemolytic (non-AMR) scenarios. The haemolytic ARRA predicted an average probability of illness of 2.9 × 10−4 and 4.5 × 10−5 per serving for the farm-to-home and retail-to-home chains, respectively, translating to 57 and 148 cases annually. The ratios of the average probability of illness per year for the three ARRAs to the haemolytic ARRA were 1.1 × 10−2 and 3.0 × 10−4 (ampicillin and penicillin G, respectively) for the farm-to-home chain and 1.3, 1.6 and 0.4 (ampicillin, penicillin G and tetracycline, respectively) for the retail-to-home chain. Sensitivity analysis showed that the initial concentrations of haemolytic V. parahaemolyticus in the gills and intestines of the fish and the cooking and washing of the fish cavity were the major variables influencing risk outputs in all modelled ARRAs. The findings of this study are useful for relevant stakeholders to make informed decisions regarding risk management to improve overall food safety.
... Indiscriminate use of antibiotics in aquaculture without following the recommended withdrawal periods not only leads to the emergence of antibiotic-resistant bacteria but also results in the occurrence of antibiotic residues in fishery products (Cabello 2006). Moreover, the "hammer-like" approach of antibiotics kills even the beneficial microbiota of the host and environment, thus causing the microbial disturbance in the culture system (Cabello 2006;Igbinosa 2016). ...
... Indiscriminate use of antibiotics in aquaculture without following the recommended withdrawal periods not only leads to the emergence of antibiotic-resistant bacteria but also results in the occurrence of antibiotic residues in fishery products (Cabello 2006). Moreover, the "hammer-like" approach of antibiotics kills even the beneficial microbiota of the host and environment, thus causing the microbial disturbance in the culture system (Cabello 2006;Igbinosa 2016). Among the various strategies to combat antibiotic resistance bacterial pathogens, bacteriophage (or phage) based innovations constitutes a promising solution. ...
This study evaluated the potential pathogenicity and antimicrobial resistance (AMR) of Vibrio species isolated from inland saline shrimp culture farms. Out of 200 Vibrio isolates obtained from 166 shrimp/water samples, 105 isolates were identified as V. parahaemolyticus and 31 isolates were identified as V. alginolyticus and V. cholerae, respectively. During PCR screening of virulence-associated genes, the presence of the tlh gene was confirmed in 70 and 19 isolates of V. parahaemolyticus and V. alginolyticus, respectively. Besides, 10 isolates of V. parahaemolyticus were also found positive for trh gene. During antibiotic susceptibility testing (AST), very high resistance to cefotaxime (93.0%), amoxiclav (90.3%), ampicillin (88.2%), and ceftazidime (73.7%) was observed in all Vibrio species. Multiple antibiotic resistance (MAR) index values of Vibrio isolates ranged from 0.00 to 0.75, with 90.1% of isolates showing resistance to ≥ 3 antibiotics. The AST and MAR patterns did not significantly vary sample-wise or Vibrio species-wise. During the minimum inhibitory concentration (MIC) testing of various antibiotics against Vibrio isolates, the highest MIC values were recorded for amoxiclav followed by kanamycin. These results indicated that multi-drug resistant Vibrio species could act as the reservoirs of antibiotic resistance genes in the shrimp culture environment. The limited host range of 12 previously isolated V. parahaemolyticus phages against V. parahaemolyticus isolates from this study indicated that multiple strains of V. parahaemolyticus were prevalent in inland saline shrimp culture farms. The findings of the current study emphasize that routine monitoring of emerging aquaculture areas is critical for AMR pathogen risk assessment.
... However, the misuse of these antibiotics has resulted in long-lasting leftovers in aquatic habitats and soil sediments. In turn, this leads to antibiotic resistance [13]. The capability of bacteria to withstand a variety of these antimicrobials enhances additional virulence factors, resulting in the appearance of multiple forms of antibiotic resistance (MAR) in Aeromonas spp. ...
The genus Aeromonas is widely distributed in aquatic environments and is recognized as a potential human pathogen. Some Aeromonas species are able to cause a wide spectrum of diseases, mainly gastroenteritis, skin and soft-tissue infections, bacteremia, and sepsis. The aim of the current study was to determine the prevalence of Aeromonas spp. in raw fish markets and humans in Zagazig, Egypt; identify the factors that contribute to virulence; determine the isolates’ profile of antibiotic resistance; and to elucidate the ability of Aeromonas spp. to form biofilms. The examined samples included fish tissues and organs from tilapia (Oreochromis niloticus, n = 160) and mugil (Mugil cephalus, n = 105), and human skin swabs (n = 51) and fecal samples (n = 27). Based on biochemical and PCR assays, 11 isolates (3.2%) were confirmed as Aeromonas spp. and four isolates (1.2%) were confirmed as A. hydrophila. The virulence genes including haemolysin (hyl A) and aerolysin (aer) were detected using PCR in A. hydrophila in percentages of 25% and 50%, respectively. The antimicrobial resistance of Aeromonas spp. was assessed against 14 antibiotics comprising six classes. The resistance to cefixime (81.8%) and tobramycin (45.4%) was observed. The multiple antibiotic resistance (MAR) index ranged between 0.142–0.642 with 64.2% of the isolates having MAR values equal to 0.642. Biofilm formation capacity was assessed using a microtiter plate assay, and two isolates (18.1%) were classified as biofilm producers. This study establishes a baseline for monitoring and controlling the multidrug-resistant Aeromonas spp. and especially A. hydrophila in marine foods consumed in our country to protect humans and animals.
... Antibiotics were the first approach used to treat and control Phdp infections, but Phdp became resistant to many antimicrobials [1]. Furthermore, there are huge concerns in using antibiotics to treat infections in aquaculture, because it can result in antibiotic residues in the final product and in the emergence and spreading of antibiotic resistance among bacterial species [14][15][16]. In this context, vaccination emerged as the most promising approach to control Phdp disease outbreaks. ...
Photobacterium damselae subsp. piscicida (Phdp) is a Gram-negative fish pathogen with worldwide distribution and broad host specificity that causes heavy economic losses in aquaculture. Although Phdp was first identified more than 50 years ago, its pathogenicity mechanisms are not completely understood. In this work, we report that Phdp secretes large amounts of outer membrane vesicles (OMVs) when cultured in vitro and during in vivo infection. These OMVs were morphologically characterized and the most abundant vesicle-associated proteins were identified. We also demonstrate that Phdp OMVs protect Phdp cells from the bactericidal activity of fish antimicrobial peptides, suggesting that secretion of OMVs is part of the strategy used by Phdp to evade host defense mechanisms. Importantly, the vaccination of sea bass (Dicentrarchus labrax) with adjuvant-free crude OMVs induced the production of anti-Phdp antibodies and resulted in partial protection against Phdp infection. These findings reveal new aspects of Phdp biology and may provide a basis for developing new vaccines against this pathogen.
... In 2013, global shrimp production dropped 10 % due to AHPND [12]. Furthermore, the use of antibiotics to treat infections in aquaculture has been discouraged due to the negative impact of its intensive application on the environment and human health and the growing emergence of resistant strains [13][14][15][16]. ...
Litopenaeus vannamei, the Pacific whiteleg shrimp, is one of the most marketable species in aquaculture worldwide. However, it is susceptible to different infections causing considerable losses in production each year. Consequently, using prebiotics that promotes the proliferation of beneficial bacteria and strengthen the immune system is a current strategy for disease control. In this study, we isolated two strains of E. faecium from the gut of L. vannamei fed with agavin-supplemented diets. These isolates showed antibacterial activity against Vibrio parahaemolyticus, Vibrio harveyi and Vibrio alginolyticus, most likely due to peptidoglycan hydrolase (PGH) activity. Furthermore, we sequenced the genome of one isolate. As a result, we observed three proteins related to the production of bacteriocins, a relevant trait for selecting probiotic strains since they can inhibit the invasion of potential pathogens. Additionally, the genome annotation showed genes related to the production of essential nutrients for the host. It lacked two of the most common factors associated with virulence in Enterococcus pathogenic strains (esp and hyl). Thus, this host-probiotic-derived strain has potential application not only in shrimp health but also in alternative aquatic environments, as it is adapted to coexist within the gut shrimp microbiota, independently of the diet.
... The phage therapy was shown as a potential solution for the antibiotic resistance crisis in clinical medium (Golkar 2014;Berglund, 2015). In wastewater treatment systems, microbial communities may increase genetic diversity linked to antibiotic resistance, and wastewater eluents may consequently impact microorganisms entering the environment and ecological systems (Sorum, 2006), thus impacting pathogen transmission to humans and animals (Brüssow and Kutter, 2005;Cabello, 2006). Inadequate treatment of municipal wastewater may increase the conditions that promote microbial antibiotic resistance through new mutations (Courvalin, 2001). ...
... However, studies have confirmed that overuse of antibiotics in shrimp farming has resulted in the evolution of several types of resistant Vibrio spp. [18], and they could also destroy microbially mature systems combined with their ineffectiveness against luminescent V. harveyi [19]. Florfenicol (FLO), one of the most widely used antibacterial drugs, penetrates the cells via facilitated transport by blocking the union site of the 50S ribosomal subunit. ...
The outbreaks caused by Vibrio spp. are a notable threat to the potential growth of the economy of penaeid culture, which is still controlled by the administration of antibiotics. At first, the infected group was subjected to phenotypic bacteriological examination with subsequent molecular identification via 16S rRNA gene sequencing, which confirmed four strains of Vibrio spp., V. atlanticus, V. natriegens, V. alginolyticus, and V. harveyi, from moribund-infected shrimp during mortality events in an Egyptian hatchery. To better understand the defense mechanism of the most effective antibiotic against Vibrio strains, the immune responses were compared and evaluated in infected Litopenaeus vannamei broodstock after being fed 5 mg kg−1 of florfenicol antibiotic, which was first determined through in vitro antibiogram tests. Therefore, our study aimed to determine the immune response of L. vannamei during Vibrio spp. infection in Egyptian hatcheries and after antibiotic medication. The parameters assessed were the total and differential hemocyte count (THC), granular cells (GC), semi-granular cells (SGC), and hyaline cells (HC). As well as the metabolic and immune enzymes: alanine aminotransferases (ALT), aspartate aminotransferases (AST), alkaline phosphatase (ALP), acid phosphatase (ACP), and lysozyme activity; an antioxidant index, such as superoxide dismutase (SOD) and glutathione (GSH); a phagocytic assay; changes in reactive oxygen species (ROS); and bactericidal activity in the hemolymph of the control, infected, and treated groups. Further evaluation of the mRNA expression levels of the prophenoloxidase (LvproPO), toll-like receptor 1 (LvToll1), and haemocyanin (LvHc) genes were performed in the hepatopancreas of the same groups. A significant drop in the THC, GC, SGC, and HC counts, as well as lysozyme and bactericidal activities, phagocytic assay, ROS, SOD, and GSH index, were represented in infected shrimp compared to control shrimp; however, a marked increase in the activity of ALT, AST, ALP, and ACP was observed. These activities were significantly restored in the treated shrimp compared to the infected shrimp. Nevertheless, no significant changes were noted in the transcriptional levels of the LvproPO and LvToll1 genes in the treated shrimp when compared to the infected shrimp; however, a significant suppression of the LvHc gene was noted. Our study aimed to determine the immune response of L. vannamei during Vibrio spp. infection in Egyptian hatcheries and after antibiotic medication. We concluded that florfenicol in medicated feed could be effective in controlling vibriosis and ameliorating the immune response of shrimp.
... The routine practice of using antibiotics for treatment and prevention of the spread of bacterial fish pathogens is a common trend; however, their abuse (over or misuse) will lead to serious problems owing to their negative impacts on human beings who consume antibiotic-treated fish and shrimp [12,13], the appearance of antibiotic-tolerant strains [14], and aquatic environmental risks [15,16]. For these reasons, researchers are interested in finding profitable, natural, and environmentally harmless antibiotic alternatives to ensure antibiotic-free and safe aquaculture. ...
The dietary effects of walnut leaf extract (WLE) on the growth, immunity, and resistance of Oreochromis niloticus to bacterial infection have been investigated. Five diets were prepared with various WLE doses of 0, 250, 500, 750, and 1000 mg/kg, termed Con (control), WLE250, WLE500, WLE750, and WLE1000, respectively. Fish (11.67 ± 0.21 g) were fed these diets for 60 days and then challenged with Plesiomonas shigelloides. Before the challenge, it was observed that dietary WLE did not significantly affect the growth, blood proteins (globulin, albumin, and total protein), and liver enzyme (ALT and AST) activities. The WLE250 group significantly increased serum SOD and CAT activities more than other groups. The serum immunological indices (lysozyme and myeloperoxidase activities) and hematological parameters (phagocytic activity %, phagocytic index, respiratory burst activity, and potential activity) were significantly increased in the WLE groups compared with the Con group. The expression of IgM heavy chain, IL-1β, and IL-8 genes were significantly upregulated in all WLE-supplemented groups in comparison with the Con group. The fish survival rates (SR; %) post challenge in the Con, WLE250, WLE500, WLE750 and WLE1000 groups were 40.0%, 49.3%, 86.7%, 73.3%, and 70.7%, respectively. The Kaplan-Meier survivorship curves illustrated that the highest SR% was found in the WLE500 group (86.7%) amongst the other groups. Accordingly, we can suggest that feeding O. niloticus with a diet supplied with WLE at a dose rate of 500 mg/kg over 60 days might enrich haemato-immune responses and increase the fish survival against the challenge with P. shigelloides. These results recommend using WLE as a herbal dietary supplement to substitute antibiotic use in aquafeed.
... In order to prevent and treat vibriosis, antibiotics are widely used in aquaculture. Long-term abuse of antibiotics not only causes pollution to the surrounding water environment, but also induces broad-spectrum drug resistance of Vibrio, and it even threatens other higher life forms by accumulating poisonous compounds in edible organisms like fish, shrimp, and shellfish (Cabello, 2006). According to researches, fish vaccines are both safer and more effective than antibiotics at reducing the spread of infectious illnesses in fish used for aquaculture (Alexandra, 2019;Fu et al., 2021). ...
Vibrio alginolyticus is the main pathogen causing vibriosis in pearl gentian grouper, which has caused significant financial losses to farmers. To develop a sustainable and effective subunit vaccine for the prevention and control of vibriosis, Lrp recombinant protein from V. alginolyticus was expressed and purified in this study. Western Blotting and ELISA demonstrated that Lrp recombinant protein with relatively higher antigenicity in V. alginolyticus can be used as an antigen for the subunit vaccine. Chitosan oligosaccharide (COS) is a very potential aquatic vaccine adjuvant to boost the immunological protection of the vaccine. Therefore, to evaluate the immune response and protection of the subunit vaccine against V. alginolyticus in pearl gentian grouper, we designed the Lrp group and Lrp+COS group as experimental groups with PBS as the control group. Immunological testing revealed that grouper serum from the experimental group had significantly higher levels of the particular antibody IgM, lysozyme (LZM), catalase (CAT), and superoxide dismutase (SOD) than serum from the control group. Additionally, groupers from the experimental group showed higher immune gene expression levels, namely IgM , CD8α , MHC-Iα , IL-1β , IL-16 , and TNF-α . After the challenge experiment, the immune protection rates of the Lrp group and Lrp+COS group were respectively enhanced to 60% and 72%. The aforementioned findings demonstrated that the Lrp+COS group’s immunological impact was superior to that of the Lrp group. Therefore, the Lrp+COS subunit vaccine is a promising candidate for the prevention and management of vibrio infection in pearl grouper.
... CIP belongs to the quinolones, a family of broad-spectrum, systemic antibacterial agents that act by inhibiting DNA gyrase (gyrA and gyrB) and DNA topoisomerase IV (parC and parE), which are required for bacterial mRNA synthesis and DNA replication [7]. Due to excessive antibiotic use and misuse in humans, agriculture and aquaculture systems, antibiotic resistance emerged and evolved in bacteria, including Vibrio species, during the past few decades [8]. Bacteria often combine more than one mechanism to increase drug resistance acquisition efficacy. ...
Background. Quinolones are commonly used for reducing the duration of diarrhea, infection severity, and limiting further transmission of disease related to Vibrio cholerae, but V. cholerae susceptibility to quinolone decreases over time. In addition to mutations in the quinolone-resistance determining regions (QRDRs), the presence of qnr and other acquired genes also contributes to quinolone resistance. Results. We determined the prevalence of quinolone resistance related genes among V. cholerae O139 strains isolated in China. We determined that eight strains carried qnrVC, which encodes a pentapeptide repeat protein of the Qnr subfamily, the members of which protect topoisomerases from quinolone action. Four qnrVC alleles were detected: qnrVC1, qnrVC5, qnrVC12, and qnrVC9. However, the strains carrying qnrVC1, qnrVC5, and qnrVC12 were ciprofloxacin (CIP)-sensitive. Contrastingly, the strain carrying qnrVC9 demonstrated high CIP resistance. qnrVC9 was carried by a small plasmid, which was conjugative and contributed to the high CIP resistance to the receptor V. cholerae strain. The same plasmid was also detected in V. vulnificus. The qnrVC1, qnrVC5, and qnrVC12 were cloned into expression plasmids and conferred CIP resistance on the host V. cholerae O139 strain. Conclusions. Our results revealed the contribution of quinolone resistance mediated by the qnrVC9 carried on the small plasmid and its active horizontal transfer among Vibrio species. The results also suggested the different effects of qnrVC alleles in different V. cholerae strains, which is possibly due to differences in sequences of qnrVC alleles and even the genetic characteristics of the host strains.
... A substantial dependence on the use of veterinary medicines has been on the increase of recent years. Application of antibiotics has led to a strong selection pressure on resistance on bacteria which adapted to this situation (Cabello, 2006;Yousefian and Amiri, 2009). The ban by regulatory bodies prohibiting the use of antibiotics in animal husbandry has made aquaprenuers seek for alternatives. ...
The influence of prebiotic, probiotic and symbiotic diet on microbial proliferation was studied using an in vitro method. In the present trial, formulated diets were supplemented with prebiotic (Sargassum muticum), probiotic (Parkia biglobosa) and combination of Parkia biglobosa and Sargassum muticum (symbiotic diet). Bacteria proliferation in supplemented feeds, small and large intestine of the African catfish, Clarias gariepinus fed the formulated diets were evaluated. The feeding trial that lasted 12 weeks was conducted in plastic aquaria, with each treatment replicated three times. A control diet containing only the feed ingredients was also formulated and fed for the same period. The result showed bacteria proliferation was lowest in the control diet and highest in feed supplemented with prebiotic. Low bacteria proliferation was observed in the small intestine of fish fed symbiotic diet while highest proliferation was recorded in the fish fed prebiotic diet. The result also revealed the lowest bacteria proliferation in the large intestine of fish fed symbiotic diet and highest in fish fed probiotic diet. Using the cell morphology and biochemical characteristics of bacteria isolates in supplemented feed, Clarias gariepinus small and large intestine, the result indicated the presence of some Lactic Acid Bacteria (LAB) known to produce a variety of antimicrobial substances which are able to stop the development of foodborne diseases by inhibiting the growth of food spoilage and pathogenic organisms.
... To be regarded as having probiotic properties, a probiotic must not harbor acquired and transferable antibiotic-resistance genes [65]. In this study, all of the bacterial isolates showed resistance to certain antibiotics used. ...
Nile tilapia is one of the most consumed farmed fish in the world. The outbreak of pathogenic bacterial diseases causes high mortality rates and economic losses in Nile tilapia farming. Antibiotic administrations are commonly utilized to inhibit and prevent bacterial infections. However, antibiotics are expensive and cause serious concerns for antibiotic resistance in fish that can be potentially transferred to humans. As an alternative solution, probiotics can be used to prevent infection of pathogenic bacteria in fish. In this work, both bacteria and yeast were isolated from fish gastrointestinal tracts and their inhibitory activity against Nile tilapia pathogenic bacteria was evaluated, as well as other probiotic properties. In this study, 66 bacteria and 176 acid tolerant yeasts were isolated from fish gastrointestinal tracts. Of all isolated microorganisms, 39 bacterial and 15 yeast isolates with inhibitory effect against pathogens were then examined for their probiotic properties (acidic and bile salt resistance, adhesion potential, and biofilm formation), formation of antibacterial factor survival rate under simulated gastrointestinal fluid, and safety evaluation. AT8/5 bacterial isolate demonstrated probiotic properties and the highest inhibition against all 54 tested pathogens while YON3/2 yeast isolate outperformed the inhibitory effect among all yeast isolates. These two probiotic isolates were further identified by 16S rDNA and the D1/D2 domain of 26S rDNA sequence analysis for bacterial and yeast identification, respectively. AT8/5 and YON3/2 showed the highest similarity to Lactiplantibacillus argentoratensis and Candida tropicalis, respectively. This is the first report on isolated L. argentoratensis and C. tropicalis with antipathogenic bacteria of Nile tilapia properties. Collectively, AT8/5 and YON3/2 could be potentially used as promising alternatives to existing antibiotic methods to prevent pathogenic bacteria infection in Nile tilapia farming.
... Furthermore, the use of disinfectants and antimicrobial drugs had limited success in the prevention or cure of aquatic diseases (Sakai et al., 1991;Gulliver et al., 1999;Sakai, 1999;Michael, 2001;Salisbury et al., 2002). The pathogens may also transfer their antibiotic-resistance genes into human pathogenic bacteria thus posing a threat to human health and environmental problems (Smith et al., 1994;Alderman and Hastings, 1998;MacMillan, 2001;Abutbul et al., 2004;Cabello, 2006), leading to failure of antibiotic treatment in some life-threatening conditions which limits the use of traditional therapeutic substances (Miranda and Zimelman, 2001;Radu et al., 2003). ...
Mango bark extract was assessed for its physiological effect on the hematology and organo-somatic indices of Clarias gariepinus, as well as its ability to resist Pseudomonas aeruginosa infection. Two diets were prepared: a control diet C and a medicated diet (M) that has mango bark extract incorporated to the control diet at 50ml/kg. One hundred and thirty-five (135) C. gariepinus of weight 117 ±0.34g were distributed into three groups as follows:- group C, fish fed control diet; group M, fish fed mango bark extract incorporated diet continuously and group M/C, fish fed mango bark incorporated diet and control diet intermittently. All groups were in triplicates. Blood samples were collected from the three groups after 3 and 6 weeks of feeding to ascertain the physiological effects of the diets on the hematology and organosomatic indices of C. gariepinus. At the end of 6 weeks feeding exercise experimented C. gariepinus was injected P. aeruginosa and observed for 21 days to ascertain the prophylactic effect of the mango bark extract on the hematology, organosomatic indices and diseases resistance ability of C. gariepinus. The results of the hematology at the end of weeks 3 and 6 of the feeding exercise shows that all the values were within a normal range of aquaculture practice and the result of the organosomatic indices (HSI, CSI and SSI) shows that the mango bark extract did not impact any pathological changes in the liver, heart and spleen, which is an indication of non-toxicity. The increased level of lymphocytes in the treated groups is indicative of immune stimulation by the mango bark extract. There was increase in the post-infection values of all the hematological parameters in the treated groups (M and M/C) and a significant reduction in the post-infection values of the control group C. The HSI of the fish in M and M/C were unchanged after the infection period while that of the control group C was significantly high. The unchanged HSI and high hematological parameters after the infection show that the mango bark extract is a strong antibacterial and liver anti-inflammatory agent for C. gariepinus.
... It is also a well-known fact that intensive production of fish in ponds can be conducive to the rapid spread of infections, and that antibiotics are often used in aquaculture by adding them to fish feed. As a consequence of the mentioned treatment, there is an increase in the concentration of antibiotic residues in the water and the sediment [18]. Björklund et al. [19] examined the presence of residues and persistence of oxytetracycline in wild fish and sediment from two ponds, after the treatment of fish with this antibiotic. ...
The aim of the present work was to examine the effect of using slaughterhouse wastewater on the production of carp meat safe for human consumption in terms of antibiotic residue level. The obtained results of the content of tetracycline and sulfonamides in water, sediment, and carp meat samples showed that the measured values were below the limit of detection for each tested parameter. Control of antibiotic residues in foods of animal origin is very important and mandatory to protect the health of end consumers and prevent the spread of antibiotic resistance.
... Residues of antibiotics have also been identified from fishery products (Sørum, 2006). Extended uses of antibiotics in veterinary medicine and agriculture practices have also been identified to provoke selection of resistance genes and spread of resistant bacteria into aquaculture (Aarestrup, 2005;Cabello, 2006). Suboptimal rapid diagnostics and suboptimal preventative medicines and vaccines are also other important factors that cause rise in antibiotic usage. ...
Ornamental fisheries are a multibillion business and livelihood of many, especially in the developing countries. India also plays an important role in ornamental fisheries and stands at 26th position in the international ornamental fish trade. Though the sector is flourishing with advanced hatchery technologies, there have been also anomalies in profit making in the sector due to fish diseases and associated mortality. The incidence of diseases in ornamental fishes, especially bacterial infections, are common and it adversely affects the export. To overcome the economic loss, farmers frequently use antibiotics in aquaculture systems which have been identified as a major driver for antimicrobial resistance (AMR). AMR is now considered a hot topic as there are no strict rules and regulations for the use of antibiotics in ornamental fisheries unlike that in edible fish culture. There have been increasing reports of resistance development and transfer of antibiotic resistance genes (ARGs) in both Gram-negative and Gram-positive bacterial pathogens as well as environmental bacteria that is known to have a colossal impact on the aquatic ecosystem. This chapter summarizes the major drivers of AMR in ornamental fisheries and the challenges, diversity of antimicrobial-resistant bacteria, modes of resistance acquisition, and lastly different management strategies and alternative approaches to reduce AMR.
... Today, fish producers use vaccines, synthetic drugs and chemicals in order to prevent such losses and make production system efficient (Lalumera et al. 2004;Ji et al. 2007;Larragoite et al. 2016;Karga et al. 2020). However, there exist several adverse effects of these synthetic and chemical products on farmed animals (Serrano 2005;Cabello 2006;Defoirdt et al. 2011). In addition, similar negative impacts have been indicated on aquatic organisms (Defoirdt et al. 2007;Baquero et al. 2008). ...
In a feeding experiment for 75 days, the effects of fumitory (Fumaria officinalis) extract on growth, haematology, immune response and antioxidant enzyme activities in rainbow trout (Oncorhynchus mykiss) were evaluated. The aqueous methanolic extract of the plant was mixed with feeds at three different levels, 0.1% (FO1), 0.2% (FO2) and 0.3% (FO3), and feed with no plant extract donated as the control. All four groups (mean initial weight: 13.02 ± 0.02 g) were fed with the prepared diets twice daily ad libitum in a triplicate experiment. Blood and liver samples were taken from the fish on 15, 30, 45, 60 and 75 days. Also, overall growth parameters were determined based on body weight data recorded from all fish before and at the end of feeding trial. Results indicated that there were variations in nonspecific immune parameters (lysozyme, myeloperoxidase and oxidative radical production), but supplementation of the plant extract did not affect the immune response of the fish significantly. On the other hand, there was a general increase in the antioxidant enzyme activities (superoxide dismutase, catalase, glutathione peroxidase, and glucose-6-phosphate dehydrogenase) evaluated in this study. Furthermore, possibly the most remarkable finding of the study is that the growth performance in the FO3 group was roughly 30% higher than that of the control group. Considering all findings in the present study, we conclude that 0.3% supplementation of fumitory extract would be beneficial for rainbow trout farming with respect to elevated growth and antioxidant status.
... Antibiotics are frequently used to treat various bacterial infections in fish farms. Due to these treatments, the effectiveness of antibiotics is becoming more limited, and the emergence of multidrug-resistant pathogens is now a global concern in the aquaculture sector [5,6]. In Canada, antibiotic treatments to fight against A. salmonicida subsp. ...
Plasmids that carry antibiotic resistance genes occur frequently in Aeromonas salmonicida subsp. salmonicida, an aquatic pathogen with severe consequences in salmonid farming. Here, we describe a 67 kb plasmid found in the A. salmonicida subsp. salmonicida Strain SHY15-2939 from Quebec, Canada. This new plasmid, named pAsa-2939 and identified by high throughput sequencing, displays features never found before in this bacterial species. It contains a transposon related to the Tn21 family, but with an unusual organization. This transposon bears a catB3 gene (chloramphenicol resistance) that has not been detected yet in A. salmonicida subsp. salmonicida. The plasmid is transferable by conjugation into Aeromonas hydrophila, but not into Escherichia coli. Based on PCR analysis and genomic sequencing (Illumina and PacBio), we determined that the transposon is unstable in A. salmonicida subsp. salmonicida Strain SHY15-2939, but it is stable in A. hydrophila trans-conjugants, which explains the chloramphenicol resistance variability observed in SHY15-2939. These results suggest that this bacterium is likely not the most appropriate host for this plasmid. The presence of pAsa-2939 in A. salmonicida subsp. salmonicida also strengthens the reservoir role of this bacterium for antibiotic resistance genes, even those that resist antibiotics not used in aquaculture in Québec, such as chloramphenicol.
... However, several factors may have a major impact on aquaculture production, among them, overcrowding or highdensity stocking of fish, accompanied by lack of hygiene, changes in temperature, inadequate water treatment and reduced nutritional levels. [3][4][5] This potentially stressful environment adversely affects the health of cultured fish, leading to immune suppression and making these fish highly vulnerable to infectious diseases. 6,7 For instance, infectious disease outbreaks that occurred during the last two decades have represented a major constraint in the aquaculture industry. ...
In recent decades, microalgal biotechnology has become one of the most valuable sources of functional feed additives. Many microalgae, such as Chlorella sp., Tetraselmis sp., Navicula sp., Phaeodactylum tricornutum, Porphyridium cruentum, Nannochloropsis gaditana, Dunaliella salina, Lobosphaera sp. and Schizochytrium sp., have been considered valuable in fish species as they enhance immunostimulant abilities, resistance against infectious diseases and tolerance to environmental stress. For instance, immunological parameters (i.e., respiratory burst activity, phagocytic capacity and IgM production) and immune‐related gene expression (i.e., proinflammatory cytokines) in fish have been manly analysed, demonstrating modulation upon microalgal administration. Moreover, disease resistance to microbial pathogen challenges has also been evidenced in several studies. In this context, the present literature review aims to assemble and reveal published research about the immunostimulant properties of some microalgae and their compounds in the immune systems of farmed fish species, whether model or new, with a high potential for aquaculture. Overall, it remains unclear how microalgae or their bioactive compounds may induce or modulate signals in the immune systems of fish species; however, the inclusion of different microalgal species in fish feed has improved the immune response and increased survival to stress conditions and infectious challenges.
... Awareness of the antibiotic susceptibility of the bacteria is crucial for the proper management of the diseases caused by these bacteria. Earlier, the global utilization of antibiotics in aquaculture and the probable transmission of resistant bacteria among earthbound and aquatic species were well documented (32,33). Nonetheless, numerous studies demonstrated antimicrobial resistance (AMR) transmission between humans and terrestrial food animals with less consideration of the aquatic ecosystem (34,35). ...
The aquaculture industry is one of the fastest-growing sectors in the food industry. The Nile tilapia, Oreochromis niloticus, is an important and inexpensive species of fish. A study was conducted to determine the effects of divergent dietary crude proteins on fish growth performance and antibiotic susceptibility of bacterial pathogens infecting all-male tilapia (Oreochromis niloticus). Forty-eight fish samples were grouped into three groups based on crude protein percentages, including 15%, 30%, and 45%, and the fish's body weight and length were measured on days 15, 30, 45, and 60. Ordinary one-way ANOVA (Tukey's multiple comparison test) was applied to three divergent dietary crude protein groups for the examination of growth performance at different time points. Using the same fish samples, bacterial strains were isolated from fish skin and gills and identified based on their morphological characteristics and biochemical testing. Kirby Bauer's disc diffusion method was used to determine the antibiotic susceptibility of identified bacterial isolates. The ANOVA (Tukey's multiple comparison test) results showed that 45% crude protein level in fish feed led to a greater growth rate than 15% and 30% under high-performance conditions. The antibiotic susceptibility findings indicate that Staphylococcus aureus showed the highest sensitivity (50%) toward antibiotics while Pseudomonas aeruginosa showed the least susceptibility (10%). The study provides a new perspective on the impact of crude protein on fish growth performance, as well as baseline information for the management of fish diseases based on antibiotic sensitivity.
... Antibiotics from multiple anthropogenic activities enter freshwater systems via various sources including wastewater effluent, surface runoff from agriculture, and aquaculture (Cabello, 2006;Czekalski et al., 2014;Dolliver and Gupta, 2008;Michael et al., 2013;Schar et al., 2020). This has contributed to the growing problem of antimicrobial resistance (AMR) through the reduction of antibiotic efficacy, as pathogens acquire antimicrobial resistance genes (ARGs). ...
In Bangladesh, fish provide over 60% of animal-source food with 56.2% of this coming from aquaculture produced predominantly in rural freshwater ponds. Increasing demand for fish products is driving intensification and resulting in higher disease prevalence, posing a risk to food security. Biosecurity is often absent in rural aquaculture practices in Bangladesh and antibiotics are commonly used to treat and prevent disease outbreaks. Antibiotics are often administered incorrectly - a key factor associated with the development of antimicrobial resistance (AMR). AMR can be disseminated rapidly within microbial ecosystems via mobile genetic elements, posing a risk for humans and animals infected with AMR pathogens as treatments with antibiotics become ineffective. Early AMR detection and understanding of the spread of antimicrobial resistance genes (ARGs) in rural aquaculture practices is critical for both food security, human health protection and food safety. Here, we apply a metagenomic approach to assess the ARG composition in pond water from six finfish (tilapia and pangasius) farms in the Mymensingh division of North-central Bangladesh. We found microbial communities within the ponds had similar alpha and beta diversities, with multiple ARGs predicted to confer resistance to eighteen different classes of antimicrobials. The most common ARGs conferred resistance to aminoglycosides and sulphonamides and were present in taxa associated with both fish and human pathogens. This ARG diversity potentially confers resistance to a wide variety of antibiotic classes and questions the effectiveness of current and future treatment of diseases with antibiotics in earthen aquaculture ponds. The microbial and ARG compositions between fish ponds within each farm were similar, which may relate to parallels in farming practices creating similar microbial selection pressures and thus comparable microbial populations. Without a more controlled approach towards antibiotic usage, we will inevitably further exacerbate the challenges in treating and preventing disease outbreaks as aquaculture production intensifies in Bangladesh.
... In recent years, with the continuous aquaculture intensification, nutrient deficiencies, antibiotic abuse and drug residues have become prevalent, and all of these undesirable factors can lead to hepatic injury in aquatic animals [1,2]. Liver injury or lesions often lead to metabolic disorders and reduced disease resistance in fish, which can easily lead to outbreaks of secondary infectious diseases and can seriously restrict the healthy development of aquaculture [3][4][5]. At present, various antibiotics, pesticides and antiviral drugs cannot effectively control the occurrence of fish liver disease [6], which has become one of the factors affecting the development of aquaculture. ...
Salvianolic acid B (Sal B), as one of the main water-soluble components of Salvia miltiorrhizae, has significant pharmacological activities, including antioxidant, free radical elimination and biofilm protection actions. However, the protective effect of Sal B on Nile tilapia and the underlying mechanism are rarely reported. Therefore, the aim of this study was to evaluate the effects of Sal B on antioxidant stress, apoptosis and autophagy in Nile tilapia liver. In this experiment, Nile tilapia were fed diets containing sal B (0.25, 0.50 and 0.75 g·kg−1) for 60 days, and then the oxidative hepatic injury of the tilapia was induced via intrapleural injection of 50 g·kg−1 cyclophosphamide (CTX) three times. After the final exposure to CTX, the Nile tilapia were weighed and blood and liver samples were collected for the detection of growth and biochemical indicators, pathological observations and TUNEL detection, as well as the determination of mRNA expression levels. The results showed that after the CTX treatment, the liver was severely damaged, the antioxidant capacity of the Nile tilapia was significantly decreased and the hepatocyte autophagy and apoptosis levels were significantly increased. Meanwhile, dietary Sal B can not only significantly improve the growth performance of tilapia and effectively reduce CTX-induced liver morphological lesions, but can also alleviate CTX-induced hepatocyte autophagy and apoptosis. In addition, Sal B also significantly regulated the expression of genes related to antioxidative stress, autophagy and apoptosis pathways. This suggested that the hepatoprotective effect of Sal B may be achieved through various pathways, including scavenging free radicals and inhibiting hepatocyte apoptosis and autophagy.
... On the other hand, the fish immune system may not be able to counteract the negative consequences of these infections, particularly when co-infections flourish simultaneously . In this case, the use of antibiotics in fish diets or the rearing water has been considered the most common interference by the veterinarians or aquaculturists to prevent and/ or control infectious diseases and reduce the mortalities and kills that may occur in fish farms as a result of the emerging diseases (Cabello, 2006;Vincent et al., 2019). However, using high amounts of antibiotics might encourage the development of antibiotic-resistant bacteria and increase environmental risks (Alderman and Hastings, 1998;Santos and Ramos, 2018). ...
The use of most antibiotics has been restricted and banned in finfish and shrimp farms due to several reasons comprising their long-lasting persistence in aquatic environments, relatively high prices, and their ability to promote the existence of antibiotic-resistant bacteria. Hence, finding economical, natural, and environmentally safe alternatives is of great importance. The use of polyphenols, polyphenol-rich plants, and plant-derived phenolic compounds for promoting aquatic animal health and welfare could be from the effective strategies for developing aquafeed and maintaining the sustainability of the aquaculture industry. Several plants are gorgeous in various bioactive functional ingredients known as phytochemicals and polyphenols. Phenolic compounds could be successfully used as natural immunostimulants in order to raise the immunity of finfish and shrimp species against several bacterial, viral, and parasitic infections and thus may replace the use of antimicrobial agents. Besides their potential roles for improvement of the growth performance, intestinal health, and enhancing the antioxidant capacity of the treated animals. Even though the trend of using plant-derived phenolic compounds is a new and leading era for the improvement of the functionality of aquafeed and the development of the aquaculture industry, there are fundamental needs and necessities to describe a clear understanding of their modes of action and potential roles in the improvement of the production rates, antioxidant activity, immune status, and disease resistance of farmed fish and shrimp.
... A number of factors have been shown to contribute to physiological changes in fish such as stress or immunosuppression thereby increasing their level of susceptibility to diseases. Some predisposing factors are overcrowding, high or sudden changes in temperature, poor water quality and poor nutritional status (Cabello, 2006). Veterinary drugs including antimicrobials are administered regularly as additives in fish food or sometimes in baths and injections and are used as prophylactics, therapeutics or growth promoters (Rico et al., 2013, Saka, Adeyemo andOdeseye, 2017). ...
This toxicological study was carried out to determine possible adverse effects of Telfairia occidentalis and Ipomoea batatas leaves in Clarias gariepinus. Ninety-six Clarias gariepinus growers (431.25±6.13 g) randomly distributed into four feeding groups were fed with herbal leaf diet containing 20 g/kg of T. occidentalis (group A), 100 g/kg of I. batatas (group B), mixture of 10 g/kg of T. occidentalis and 50 g/kg I. batatas (group C) and basal diet (group D) which served as the control group. After a 40-day feeding period, blood samples were collected for serum biochemical assay and organs were harvested for antioxidant and tissue biochemical assay. A significant decrease in creatinine was observed in the fish in group C when compared with those in group D. Also, there was no significant difference in the liver superoxide dismutase activity across all feeding groups but no significant increase in the intestinal superoxide dismutase activity of the fish in group C when compared to those in group A. There were no significant differences in the values of liver enzyme markers and lipid profile across all feeding groups. However, a significant increase in the level of intestinal malondialdehyde was observed in the fish in group B when compared with those in groups A and D. This study revealed that oral administration of a combination of T. occidentalis (10 g/kg) and I. batatas (50 g/kg) leaves enhanced antioxidant enzymes and is recommended for protection against oxidative stress in Clarias gariepinus.
... Synthetic growth promoters such as several antibiotics have been used in fish diets for decades, due to their positive effects on the growth rate, weight gain and disease prevention (Cabello, 2006). As a result, there is a need for alternative natural additives to replace synthetic growth promoters. ...
The aim of this study was to investigate the effects of dietary supplementation of γ-irradiated cinnamon ethanolic extract on the growth performance, digestive enzymes, lysozyme activity level and hematological factors in the juvenile rainbow trout. The fish were divided into five groups, including control group and four experimental groups (received diets enriched with 10 g/kg of non-irradiated or irradiated CEE at the radiation doses of 10, 20 and 40 KGy. At the end of the feeding trial (60` days), 10 fish were sampled from each tank after 12 h of feed deprivation. The results showed that the fish dietary irradiated CEE at doses of 10 KGy and 20 KGy had significantly higher final weights, weight gain, specific growth rates and growth hormone levels, and lower feed conversion ratios compared to the other groups (P≤0.05). The blood glucose level significantly lowered in the fish group fed with dietary γ-irradiated CEE, and increased the activity of lysozyme activity level and digestive enzymes compared to the control group (P≤0.05). In conclusion, dietary supplementation of γ-irradiated CEE at a dose of 10 KGy can enhance the positive effects of cinnamon extract and improve the growth performance, digestion and lysozyme activity in juvenile rainbow trout.
... Current knowledge of the impact of antibiotics used in aquaculture on the health and environment is poor, particularly in developing countries. In addition, drug residues may remain in fish used for human consumption; therefore, the antibiotics released into the environment can lead to antibiotic-resistant bacteria development in the food chain (Cabello 2006). Resistance to antibacterial agents is a global public health problem and one that is increasing as the antibacterial continues to lose effectiveness (Akinbowale et al. 2006). ...
Karimi RD, Ngeranwa JJN, Njagi ENM, Kariuki S. 2022. The bacterial flora of Oreochromis niloticus and Clarias gariepinus from earthen ponds in Sagana and Masinga, Kenya. Intl J Bonorowo Wetlands 12: 63-73. Food-borne diseases traced to fish consumption have been reported globally, including in Kenya. The aspect of food quality as far as fish consumption is concerned is underestimated in Kenya though aquaculture has been promoted. The bacterial flora of Tilapia (Oreochromis niloticus Linnaeus, 1758) and Catfish (Clarias gariepinus Burchell, 1822) from Masinga Dam and earthen ponds at Sagana fish farm was determined in this study to determine the anti-microbial response of the pathogenic bacteria. Tilapia fish and Catfish samples were collected from Masinga Dam and Sagana farm in the dry and rainy seasons. The fish were skinned, and gut content was taken for laboratory tests. The water and water sediment samples from these two study sites were also collected. Those samples were processed and cultured in MacConkey agar, and the selective media were subcultured in the colonies and then subjected to morphological examination from cultures. Then, the biochemical tests were carried out using commercially available API kits. The study showed the presence of bacterial species belonging to Enterobacter spp. (n=34), Pseudomonas spp. (n=6), Aeromonas spp. (n=5), Vibrio spp. (n=3) and Acinetobacter spp. (n=2) isolates during the dry season, while bacterial species belonging to Enterobacter spp. (n=31), Pseudomonas spp. (n=6), Aeromonas spp. (n=4) isolates during the dry season. The anti-microbial susceptibility analysis showed that the highest resistance rates were found against Ampicillin (Amp) (61.5% of isolates), Amoxicillin (AmL) (65.9% of isolates), Tetracycline (Te) (31.8% of isolates), and Chloramphenicol (C) (27.5% of isolates) while the lowest was Nalidixic acid (Na), Cefuroxime (Cxm) and Streptomycin (S) at (4.4% of isolates) each. All isolates were sensitive to Gentamycin (Gen), Ciprofloxacin (Cip), and Cefotaxime (CTX). The presence of the above organisms, some potentially pathogenic to humans, indicates that improperly handled, undercooked, or consumed raw fish may cause disease in susceptible individuals. At the same time, some isolates’ anti-microbial resistance indicates that the use of antibiotics in aquaculture to promote growth should be studied further with a view to policy formulation.
... Long-term antibiotic use in aquaculture at levels well below the minimum inhibitory concentration of the susceptible wild-type population puts pressure on microbes and also leads to horizontal gene transfer between human and fish pathogens (Gullberg et al., 2011). Since antibiotics are non-biodegradable and are comparatively stable, they pose a risk to public health by leaving residues in commercially produced fish and shellfish products for a longer period of time (Cabello, 2006). Done and Halden (2015) found traces of the antibiotic tetracycline macrolide and sulphonamide in samples of farmed salmon, tilapia, and trout from 11 nations, including the United States, China, Mexico, Thailand, Scotland, and Canada. ...
Aquaculture is evolving into a highly concentrated industry with much intensive farming. Infectious diseases are
becoming more prevalent, resulting in significant economic losses, and their treatment demands the use of antimicrobial agents. However, the use of antimicrobials in aquaculture has resulted in the emergence and spread of antibiotic-resistant bacteria and genes, as well as the presence of residues in aquaculture products and the environment. Also, the use of antibiotics as disease control agents and growth promoters in aquaculture has recently sparked significant concerns in many countries due to the potential risks to human health. As this has become a global concern, alternative therapies for bacterial pathogens in animal production, particularly in aquaculture, are required. This review article aims to present the most recent information on antibiotic use in aquaculture systems. In addition, several new alternative control measures are briefly elaborated in this review.
... Release of antibiotics in natural water bodies can make antibiotic-resistant strains, change the natural flora and fauna, and also be biomagnified throughout food chain. In addition, antibiotics and their derivatives can accumulate in the tissues of aquatic organisms, which can be dangerous to human health as a consumer [1][2][3]. Therefore, use of natural materials as alternative to chemicals can be an efficient way to enhance fish immunity and to treat diseases [4,5]. Over the last decade, the use of plant-based materials and their derivatives has increased to enhance the fish immune system [6][7][8]. ...
In this study, thymol (TYM) at dietary levels of 0, 1, 1.5, 2, and 2.5 g/kg diet was used to evaluate its effects on growth, digestive performance, immunity, and resistances to the infection induced by Streptococcus iniae in the rainbow trout, Oncorhynchus mykiss. A number of 450 fish (35.8±4.4 g; Mean±SD) were distributed to 15 tanks (30 fish/tank) in three replicates and fed TYM for 60 days. After feeding period, Fish fed 1.5-2.5 g TYM showed better growth, higher digestive enzyme activity, and body protein content compared to other diets (P
... The acquisition of resistance in bacteria or bacterial communities arises via genetic transfer events under the positive pressure of various phenomena currently on the rise, such as the environmental antimicrobial contamination [28,29] and the emergence of microenvironments with high-density microbial communities like highly anthropized aquatic environments or sewage treatment plants, where indigenous bacteria and those derived from humans and animals co-exist [30]. Naturally occurring aquatic bacteria, including pathogenic Vibrio strains, can serve as a reservoir of resistance genes and may play an important role in the evolution and spread of antibiotic resistance in aquatic environments [31][32][33][34]. Considering that seafood and especially bivalves can concentrate these bacteria, they also represent a potential reservoir of resistance genes, transmitted to humans through their consumption. ...
Seafood can vehiculate foodborne illnesses from water to humans. Climate changes, increasing water contamination and coastlines anthropization, favor the global spread of Vibrio spp. and the occurrence of antibiotic-resistant isolates. The aim of this study was to evaluate the spread of potentially pathogenic Vibrio spp. in fishery products collected in Sicily and to assess their antibiotic resistance. Bacteriological and molecular methods were applied to 603 seafood samples to detect V. parahaemolyticus, V. cholerae, V. vulnificus, and Vibrio alginolyticus in order to assess their pathogenicity and antimicrobial resistance. About 30% of bivalves and 20% of other fishery products were contaminated by Vibrio spp.; V. parahaemolyticus accounted for 43/165 isolates, 3 of which were carrying either tdh or trh; V. cholerae accounted for 12/165 isolates, all of them non-O1 non-O139 and none carrying virulence genes; and V. vulnificus accounted for 5/165 isolates. The highest rates of resistance were observed for ampicillin, but we also detected strains resistant to antibiotics currently included among the most efficient against Vibrio spp. In spite of their current low incidence, their rise might pose further issues in treating infections; hence, these results stress the need for a continuous monitoring of antimicrobial resistance among fishery products and an effective risk assessment.
... Consequently, there has been increased attention on developing innovative techniques to control and minimize the environmental impact of this activity [3,4]. Indeed, intensive mariculture of high-value carnivorous organisms can frequently lead to several environmental and sustainability issues [5][6][7][8], mainly referring to the release of organic and inorganic substances as both particulate waste and dissolved nutrients in the water column [9][10][11]. ...
Citation: Borghese, J.; Musco, L.; Arduini, D.; Tamburello, L.; Del Pasqua, M.; Giangrande, A. A Comparative Approach to Detect Macrobenthic Response to the Conversion of an Inshore Mariculture Plant into an IMTA System in the Mar Grande of Taranto (Mediterranean Sea, Italy). Water 2023, 15, 68. https://doi. Abstract: The expected bioremediation effect, driven by the conversion of an inshore mariculture plant into an Integrated Multi-Trophic Aquaculture (IMTA) system, which could mitigate the fish farm impact, related to the accumulation of organic matter on the seabed, has been studied. The ecological quality status was studied following a Before-After-Control-Impact (BACI) design and variation measured through M-AMBI and compared with the results of univariate and multivariate analyses of variance, to evaluate the sensitivity of the two methodologies. Results from M-AMBI indicated a sharp change in the ecological quality status, just after one year of the conversion of the plant. By contrast, although changes were detected also utilizing univariate and multivariate statistical analysis, the natural temporal variability characterizing the area partially masked evidence of environmental amelioration.
The exponential growth of aquaculture over the past 30 years has been accompanied by a parallel increase in the use of antimicrobials. This widespread use has had negative effects on animal, human and environmental health and affected the biodiversity of the environments where aquaculture takes place. Results showing these harmful effects have been resisted and made light of by the aquaculture industry and their scientific supporters through introduction of misunderstandings and misinterpretations of concepts developed in the evolution, genetics, and molecular epidemiology of antimicrobial resistance. We focus on a few of the most obvious scientific shortcomings and biases of two recent attempts to minimise the negative impacts of excessive antimicrobial use in Chilean salmon aquaculture on human and piscine health and on the environment. Such open debate is critical to timely implementation of effective regulation of antimicrobial usage in salmon aquaculture in Chile, if the negative local and worldwide impacts of this usage are to be avoided.
Effects of dietary Euphorbia heterophylla extract (EH) on growth performance, feed utilization and haemato-biochemical parameters in African catfish, Clarias gariepinus, juveniles were evaluated in this study. Diets fortified with EH at 0 (control), 0.5, 1.0, 1.5 or 2.0 g/kg were fed to the fish to apparent satiation for 84 days before challenging it with Aeromonas hydrophila. The weight gain, specific growth rate and protein efficiency ratio of fish fed EH-supplemented diets were significantly higher but lower feed conversion ratio (p < 0.05) than the control group. The villi height and width at the proximal, mid and the distal of the guts rose significantly with the increasing levels of EH from 0.5 to 1.5 g than the fish fed basal diet. Dietary EH enhanced (p < 0.05) the packed cell volume and haemoglobin, whereas 1.5 g EH boosted white blood cell, in relation to their counterpart in the control group. There were significant increase in the activities of glutathione-S-transferase, glutathione peroxidase and superoxide dismutase (p < 0.05) in the fish that were fed diets supplemented with EH than the control. Dietary EH also enhanced phagocytic activities, lysozyme activities and relative survival (RS) of C. gariepinus than the control group, with the highest RS obtained in fish that were fed diet containing EH at 1.5 g/kg level. These results revealed that the fish fed 1.5 g/kg dietary EH promoted growth performance, antioxidant and immune profiles, as well as protection against A. hydrophila infection.
Worldwide, consumers relish fish as food, owing to its nutritional and health benefits. Bacteria, including antimicrobial-resistant (AMR) strains, gain entry onto fish either during preharvest growth phase or postharvest processing and handling. The domestic and international trade in raw and processed fish makes them inadvertent vehicles for national and transboundary transmission of bacteria. Microorganisms in the aquatic environment adapt to the sublethal concentrations of antibiotic resulting in emergence of resistance that may eventually be disseminated via the harvested fish to human pathogens; either in the gut of fish consumers, on food contact surfaces, or in the environment. This chapter gives an overview of the importance of fish in human diet, role of fisheries in addressing food security, antimicrobial use (AMU) in aquaculture, regulations related to AMU in aquaculture, food safety vis-à-vis antibiotic residues, Rapid Alert System for Food and Feed (RASFF) notifications of the European Union pertaining antibiotic residues in fish and crustaceans, antimicrobial resistance in preharvest and postharvest fisheries, and suggest measures to mitigate AMR in aquatic animal farming.
The incidence of antimicrobial resistance (AMR) is rapidly spreading worldwide. It is depleting the repertoire of antibiotics in use but the pace of development of new antibiotics is stagnant for decades. Annually, millions of people are killed by AMR. This alarming situation urged both scientific and civil bodies to take steps to curb AMR as a top priority. Here we review the various sources of AMR in the environment, especially focusing on the food chain. Food chain inculcates pathogens with AMR genes and serves as a conduit for its transmission. In certain countries, the antibiotics are more used in livestock than in humans. It is also used in agriculture crops of high value products. The indiscriminate use of antibiotics in livestock and agriculture increased rapid emergence of AMR pathogens. In addition, in many countries nosocomial settings are spewing AMR pathogens, which is a serious health hazard. Both the developed and low and middle income countries (LMIC) face the phenomenon of AMR. Therefore, a comprehensive approach for monitoring all sectors of life is required to identify the emerging trend of AMR in environment. AMR genes' mode of action must be understood to develop strategies to reduce risk. The new generation sequencing technologies, metagenomics and bioinformatics capabilities can be resorted to quickly identify and characterize AMR genes. The sampling for AMR monitoring can be done from multiples nodes of the food chain as envisioned and promoted by the WHO, FAO, OIE and UNEP under the One Health approach to overcome threat of AMR pathogens.
Organic acids and their derivatives have been attributed to growth and well-being improvement in fish when supplemented in their diets. Therefore, this study was conducted to evaluate the ameliorative role of potassium formate (PF) in rohu Labeo rohita fingerlings. A total of 240 healthy rohu fingerlings (9.0 ± 0.5 g ± SE) were randomly divided into four equal groups in triplicates. Fish were fed with isonitrogenous feeds: PF10 (10 g PF/kg), PF20 (20 g PF/kg) and PF30 (30 g PF/kg). Feed without PF supplementation served as control. The results indicated that the specific growth rate (SGR) and feed conversion ratio (FCR) were significantly (p<0.05) higher in PF10. Total serum globulin content was found significantly (p<0.05) elevated in PF10 after the bacterial challenge. Non-specific lysozyme activity was significantly higher (p<0.05) after the challenge. The digestive protease enzyme activity was significantly (p<0.05) improved in PF10 treatment. Additionally, the digestive morphology of the treated fish was seen to be improved. Greater villus area, increased villus number, reduced lumen space in the hindgut, reduced vacuolation in mucosal folds and proliferation of goblet cells-like changes were observed in the PF-supplemented fish. Significantly (p<0.05), a higher relative percentage of survival (RPS) was observed in PF10 and PF20 treatments. The study revealed that the dietary supplementation of rohu fingerlings with lower levels of potassium formate could enhance the nutritional efficiency and physiological activities of rohu fingerlings. This study serves as a baseline for future research on the application of formic acid derivatives and other acidifiers in carp culture.
Maternal exposure to antibiotics existing in the environment is a predisposing factor for developmental malformation with metabolic disorders in offspring. In this study, female zebrafish (3 months) were exposed to 0.05 mg/L and 0.5 mg/L florfenicol (FF) for 28 days. After pairing and spawning with healthy male fish, F1 embryos were collected and developed to 5 d post-fertilization (dpf) in clear water. And the adverse effects on the F1 generation were examined thoroughly. The fecundity of F0 female fish and the hatchability, mortality, and body length of F1 larvae significantly decreased in the treatment group. Meanwhile, multi-malformation types were found in the exposure group, including delayed yolk sac absorption, lack of swim bladder, and spinal curvature. Metabolomic and transcriptomic results revealed alterations in metabolism with dysregulation in tricarboxylase acid cycle, amino acid metabolism, and disordered lipid metabolism with elevated levels of glycerophospholipid and sphingolipid. Accompanying these metabolic derangements, decreased levels of ATP and disordered oxidative-redox state were observed. These results were consistent with the damaged mitochondrial membrane potential and respiratory chain function, suggesting that the developmental toxicity and perturbed metabolic signaling in the F1 generation were related to the mitochondrial injury after exposing F0 female zebrafish to FF. Our findings highlighted the potential toxicity of FF to offspring generations even though they were not directly exposed to environmental contaminants.
Graphene oxide (GO) membranes have suffered from the instability of water permeability and low rejection of pollutant separation. In this paper, a reasonable modification protocol for GO nanosheets at the molecular level was proposed. A molecular cross-linking strategy was adopted to regulate the interlayer spacing of GO nanosheets, and nanofiltration membranes with high water stability and excellent antifouling capacity were prepared, which could effectively reject antibiotics and salts. The GO1-MPD0.5 (the mass ratio of GO nanosheets to MPD is 1:0.5) and GO/GO1-MPD0.5-0.25 (the doping ratio of GO1-MPD0.5 is 25%) membranes had stable water permeability of 4.22 ± 0.06 and 3.65 ± 0.11 L m-2 h-1 bar-1, and the rejection rates for ciprofloxacin (CIP) and ofloxacin (OFX) were 93.35 ± 3.62 and 95.48 ± 2.97 and 85.89 ± 6.52 and 88.21 ± 3.67%, respectively. Molecular dynamics simulations well explained the high water stability of membranes, and the cross-linked hydrophobic benzene ring played a role in the rejection of pollutant molecules. Moreover, the GO1-MPD0.5 membrane showed excellent antifouling capacity and the flux recovery ratio (FRR) was more than 98%. This paper provides a new idea for the design of nanofiltration membranes with high stability and good rejection permeability at the molecular level and provides a prospect for the application of nanofiltration membranes in practical water treatment and water purification.
With the rise in global population and increased urbanization, the consumption of fish and fish-based by-products gained importance owing to its better and easily digestible protein constituents. Such conditions led to the generation of large amounts of fish waste and pose a detrimental effect to environment. Therefore, the concept of valorization has been introduced in the sector of fish waste management has been introduced which will maintain a cleaner production as well as lead to the production of several value-added products for human well-being. The present research study has pinpointedly discussed several valorization methods like hydrolysis, fermentation, anaerobic treatment, etc. for proper utilization of fish wastes in the manufacturing of fish-based products by pharmaceuticals, nutraceuticals-based industries. Furthermore, for the increase of coastal economy, unprecedented use of different fish growth stimulators and antibiotics are used which unknowingly release antibiotic resistance genes (ARGs) to the environment. Such ARGs lead to the development of ‘resistome’ which will impose a serious threat in the foreseeable future to environmental health. Thus, the concept of waste valorization along with environmental contaminants like ARG will open up a new vista towards proper utilization of fish wastes alongside encouraging entrepreneurs and different government organizations to develop strategies for controlling fish wastes under the circular economy model.
Keywords: Fish waste management; Valorization; Circular bioeconomy; Fish hydrolysate; ARG
Veteriner Hekimlik dünyanın en eski mesleklerinden birisidir. Yalnızca
hayvan sağlığı ile değil aynı zamanda hayvansal gıdaların uygun şekilde
insan tüketimine sunulması ve dolayısıyla halk sağlığı ile doğrudan ilişkili
bir meslek grubudur. Sağlıklı insan, sağlıklı hayvan ve sağlıklı bir dünya için
çalışan veteriner hekimlik mesleği etik değerlere bağlı bilimsel yaklaşımlarla
sağlık alanında hizmet sunmaktadır. Veteriner hekimlik mesleği, fizyolojik,
metabolik ve anatomik olarak farklı birçok hayvan türü ile ilgilenmektedir. Bu
türler arasında kanatlılar, memeliler, sürüngenler, sıcakkanlılar, soğukkanlılar,
kara hayvanları, deniz hayvanları gibi çok geniş bir alanda hizmet vermektedir.
Bu canlıların her birinin sağlıklı yaşam alanlarının oluşturulması ekosistem
içerisinde önemli yer tutmaktadır. Günümüzde ekonomik değeri olan sığır,
koyun, keçi, tavuk gibi evcil hayvanların yanı sıra kedi ve köpek gibi evcil
dostlarımız da insan hayatında büyük bir yeri kaplamaktadır. Artık birçok
evde kedi ve köpeklerle birlikte yaşanıyor olması, onların ihtiyacı olan yaşam
standartlarının da sağlanması koşulunu beraberinde getirmektedir.
“Veteriner Hekimlikte Güncel Değerlendirmeler” isimli bu kitabımızda,
alanında uzman hekimler tarafından derlenmiş özgün bilimsel konular ve
yaklaşımlar ile okuyucularına ışık tutacaktır
Carotenoid pigmentation in salmon may interfere with the accuracy of antibiotic analysis with ultra-high pressure liquid chromatography coupled to tandem spectrometry (UPLC-MS/MS) by causing matrix effects or affecting the recovery of compounds during extraction. In the present study, we used both pigmented and non-pigmented salmon to understand the role pigments play on antibiotic analysis, and tested whether clean-up of the extract with dispersive solid phase extraction (dSPE) or hydrophilic-lipophilic balance (HLB) SPE clean-up reduces matrix effects. Thirty antibiotics and their respective class-specific surrogate standards were measured in Sockeye (pigmented), King (pigmented) and Ivory King (non-pigmented) salmon extracted using the QUEChERS method, or a modified QUEChERS method involving dSPE or HLB SPE clean-up (for Sockeye salmon only). Significant matrix effects and lower percent recoveries of spiked antibiotics were observed in pigmented versus non-pigmented salmon extracted with the QUEChERS method. Dispersive SPE clean-up did not improve extraction recoveries or matrix effects. However, SPE clean-up with HLB columns improved matrix effects for several antibiotics but reduced the percent recovery to < 30%. Across all types of salmon analyzed, the accuracy of quantitation was minimally impacted, likely due to similar behavior of the surrogate standards tagged to each antibiotic class during extraction. Our results demonstrate that carotenoids in salmon are associated with significant matrix effects and low extraction recoveries, but do not impact accuracy.
Ginkgo biloba leaf extract (GBE) has been extensively used in the treatment of diseases due to its anti-inflammatory, antioxidant, and immunomodulatory effects. In aquaculture, GBE is widely used as a feed additive, which is important to enhance the immunity of aquatic animals. The current study evaluated the effects of adding GBE to the diet of Penaeus vannamei (P. vannamei) under intensive aquaculture. The GBE0 (control group), GBE1, GBE2, and GBE4 groups were fed a commercial feed supplemented with 0.0, 1.0, 2.0, and 4.0 g/kg GBE for 21 days, respectively. The results showed that dietary GBE could alleviate hepatopancreas tissue damage and improve the survival rate of shrimp, and dietary 2 g/kg GBE could significantly increase the total hemocyte count (THC), the hemocyanin content, the antioxidant gene's expression, and the activity of their encoded enzymes in P. vannamei. Furthermore, transcriptome data revealed that immunity-related genes were upregulated in the GBE2 group compared with the GBE0 group after 21 days of culture. Drug metabolism-cytochrome P450, sphingolipid metabolism, linoleic acid metabolism, glycerolipid metabolism, fat digestion and protein digestion and absorption pathways were significantly enriched, according to KEGG results. Surprisingly, all of the above KEGG-enriched pathways were significantly upregulated. These findings demonstrated that supplementing P. vannamei with 2 g/kg GBE improved its environmental adaptability by improving immunity, lipid metabolism, and detoxification. In this study, a comprehensive evaluation of the effects of dietary GBE on the intensive aquaculture of P. vannamei was conducted to provide a reference for the healthy culture of P. vannamei.
Salmonella enterica serotype typhimurium ( S. typhimurium ) DT104 (DT104) first emerged as a major pathogen in Europe and is characterized by its pentadrug-resistant pattern. It has also been associated with outbreaks in the United States. The organism typically carries resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. The mechanism of chloramphenicol resistance in DT104 was determined by producing antibiotic-resistant Escherichia coli host strain clones from DT104 DNA. DNA from chloramphenicol-resistant clones was sequenced, and probes specific for the genes flo S. typhimurium ( flo St ), int , invA , and spvC were produced for colony blot hybridizations. One hundred nine Salmonella isolates, including 44 multidrug-resistant DT104 isolates, were tested to evaluate the specificities of the probes. The gene flo St , reported in this study, confers chloramphenicol and florfenicol resistance on S. typhimurium DT104. Florfenicol resistance is unique to S. typhimurium DT104 and multidrug-resistant S. typhimurium isolates with the same drug resistance profile among all isolates evaluated. Of 44 DT104 isolates tested, 98% were detected based on phenotypic florfenicol resistance and 100% had the flo St -positive genotype. Resistances to florfenicol and chloramphenicol are conferred by the gene flo St , described in this paper. Presumptive identification of S. typhimurium DT104 can be made rapidly based on the presence of the flo St gene or its resulting phenotype.
Salmonella enterica serotype typhimurium (S. typhimurium) DT104 (DT104) first emerged as a major pathogen in Europe and is characterized by its pentadrug-resistant pattern. It has also been associated with outbreaks in the United States. The organism typically carries resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. The mechanism of chloramphenicol resistance in DT104 was determined by producing antibiotic-resistant Escherichia coli host strain clones from DT104 DNA. DNA from chloramphenicol-resistant clones was sequenced, and probes specific for the genes floS. typhimurium (floSt), int, invA, and spvC were produced for colony blot hybridizations. One hundred nine Salmonella isolates, including 44 multidrug-resistant DT104 isolates, were tested to evaluate the specificities of the probes. The gene floSt, reported in this study, confers chloramphenicol and florfenicol resistance on S. typhimurium DT104. Florfenicol resistance is unique to S. typhimurium DT104 and multidrug-resistant S. typhimurium isolates with the same drug resistance profile among all isolates evaluated. Of 44 DT104 isolates tested, 98% were detected based on phenotypic florfenicol resistance and 100% had the floSt-positive genotype. Resistances to florfenicol and chloramphenicol are conferred by the gene floSt, described in this paper. Presumptive identification of S. typhimurium DT104 can be made rapidly based on the presence of the floSt gene or its resulting phenotype.
Global production of farmed fish and shellfish has more than doubled in
the past 15 years. Many people believe that such growth relieves pressure
on ocean fisheries, but the opposite is true for some types of aquaculture.
Farming carnivorous species requires large inputs of wild fish for feed. Some
aquaculture systems also reduce wild fish supplies through habitat modification,
wild seedstock collection and other ecological impacts. On balance, global
aquaculture production still adds to world fish supplies; however, if the
growing aquaculture industry is to sustain its contribution to world fish
supplies, it must reduce wild fish inputs in feed and adopt more ecologically
sound management practices.
Industrial antibiotic usage in agribusinesses and aquaculture is the force that drives the evolution of antibiotic resistant bacteria that produce human and animal disease in many countries. Several studies have demonstrated that most of the industrial use of antibiotics is unnecessary, and that modernization and hygienic changes can reduce this use of antibiotics without negative economic impact. In Chile, industrial aquaculture of salmon has expanded rapidly in the last 20 years becoming a major export business. The exponential growth of this industry has been accompanied by an unrestricted heavy usage of antibiotics in the aquatic environments of lakes, rivers and the ocean, and its impact is being felt in the emergence of antibiotic-resistant bacteria around aquaculture sites and a decrease in the plancktonic diversity in the same areas. The passage of antibiotic resistance genes from aquatic bacteria to human and animal pathogens has been demonstrated, indicating that industrial use of antibiotics in aquaculture affects negatively the antibiotic therapy of human and animal bacterial infections. The Chilean situation triggers important concerns because it includes the use of fluoroquinolones in aquaculture, that are not biodegradable and are able to remain in the environment for years as well as being still effective in treating human infections. The use of large volumes of a wide spectrum of antibiotics in an aquatic environment heavily contaminated with human and animal pathogens also amplifies the opportunities for gene transfer among bacteria, facilitating the emergence of antibiotic resistance and more pathogenic bacterial recombinants. The detection of residual antibiotics in salmons marketed for human consumption that can modify the normal flora of the population also suggests the need for controls on this antibiotic usage and on the presence of residual antibiotics in aquaculture food products. This important problem of public health demands an active dialogue between government officials responsible for protecting public health, aquaculture industry representatives, politicians, consumers and professionals dealing with these matters (Rev Méd Chile 2004; 132: 1001-6)
From the docks of declining coastal villages to the desks of corporate and government offices, salmon farming has been hailed as a new hope for the world's ailing offshore fishing industry and a way to reduce pressure on severely depleted fish stocks. However, the aquaculture industry has grown so quickly that, in many areas - including the Pacific Northwest - it has outstripped the wherewithal to address its adverse ecological impacts. Will fish farms, in the end, do more harm than good? Or can they deliver on their sustainable promise?
There is interest in the paradigm that relates environmental sea changes to the emergence of diseases that affect both aquatic organisms in the sea and human beings. The emergence of Vibrio parahaemolyticus as an important cause of epidemic summer diarrhea in 2004 and 2005, confined mainly to the tenth region in Chile, could be a manifestation of this trend. This and other areas of the country have also experienced several outbreaks of paralytic shellfish poisoning (PSP), diarrheal shellfish poisoning (DSP) and amnesic shellfish poisoning (ASP) caused by harmful algal blooms (HAB) of Alexandrium catenella, Dinophysis acuta and Pseudonitzchia species, respectively. The short historical record of these pathological phenomena in Chile suggests that they are increasing in frequency and expanding their geographical range. The V parahaemolyticus isolates responsible for the Chilean outbreaks correspond mainly to the pandemic strain O3:K6. HAB found in Chile and the intoxications caused by them have similar biological characteristics to those described in other areas of the world. The tenth region, the area where these problems are emerging, produces approximately 80-90% of the shellfish consumed in Chile and a large proportion of the shellfish that is exported. Prevention of these public health problems can be attained by developing policies that increase environmental surveillance for Vibrios and toxic algae, improve the epidemiological surveillance of acute diarrhea and algal intoxications after the ingestion of raw bivalves, and educate the population on the mode of transmission of these diseases. Scientific capacity and laboratories need to be developed to widen the limited knowledge of the biology of Vibrio and toxic algae and the environmental factors that favor their emergence as public health and economic problems in Chile (Rev Méd Chile 2005; 133: 1081-88)
Key Words marine aquaculture, fish meal, ecological impacts, offshore aquaculture ■ Abstract With continued human pressure on marine fisheries and ocean re-sources, aquaculture has become one of the most promising avenues for increasing marine fish production in the future. This review presents recent trends and future prospects for the aquaculture industry, with particular attention paid to ocean farming and carnivorous finfish species. The benefits of farming carnivorous fish have been challenged; extensive research on salmon has shown that farming such fish can have negative ecological, social, and health impacts on areas and parties vastly separated in space. Similar research is only beginning for the new carnivorous species farmed or ranched in marine environments, such as cod, halibut, and bluefin tuna. These fish have large market potential and are likely to play a defining role in the future direction of the aquaculture industry. We review the available literature on aquaculture development of carnivorous finfish species and assess its potential to relieve human pressure on marine fisheries, many of which have experienced sharp declines.
Nucleotide sequence analysis, and more recently whole genome analysis, shows that bacterial evolution has often proceeded by horizontal gene flow between different species and genera. In bacteria, gene transfer takes place by transformation, transduction, or conjugation and this review examines the roles of these gene transfer processes, between different bacteria, in a wide variety of ecological niches in the natural environment. This knowledge is necessary for our understanding of plasmid evolution and ecology, as well as for risk assessment. The rise and spread of multiple antibiotic resistance plasmids in medically important bacteria are consequences of intergeneric gene transfer coupled to the selective pressures posed by the increasing use and misuse of antibiotics in medicine and animal feedstuffs. Similarly, the evolution of degradative plasmids is a response to the increasing presence of xenobiotic pollutants in soil and water. Finally, our understanding of the role of horizontal gene transfer in the environment is essential for the evaluation of the possible consequences of the deliberate environmental release of natural or recombinant bacteria for agricultural and bioremediation purposes.
To determine risk factors for cholera in an epidemic-disease area in South America, a case-control investigation was performed in Guayaquil, Ecuador, in July 1991. Residents > 5 years old who were hospitalized for treatment of acute, watery diarrhoea and two matched controls for each were interviewed regarding sources of water and food, and eating, drinking, and hygienic habits. Interviewers inspected homes of case-patients and controls to document water treatment, food-handling, and hygienic practices. Faecal specimens and shellfish were cultured for Vibrio cholerae O 1. Isolates were tested for susceptibility to a variety of antimicrobial agents. Drinking unboiled water (odds ratio [OR] = 4.0, confidence interval [CI] = 1.8-7.5), drinking a beverage from a street vendor (OR = 2.8, CI = 1.3-5.9), eating raw seafood (OR = 3.4, CI = 1.4-11.5), and eating cooked crab (OR = 5.1, CI = 1.4-19.2) were associated with illness. Always boiling drinking water at home (OR = 0.5, CI = 0.2-0.9) was protective against illness. The presence of soap in either the kitchen (OR = 0.3, CI = 0.2-0.8) or bathroom (OR = 0.4, CI = 0.2-0.9) at home was also protective. V. cholerae O 1 was recovered from a pooled sample of a bivalve mollusc and from 68% of stool samples from case-patients. Thirty-six percent of the isolates from stool specimens were resistant to multiple antimicrobial agents. Specific prevention measures may prevent transmission through these vehicles in the future. The appearance of antimicrobial resistance suggests the need for changes in current methods of prevention and treatment.
Salmonella typhimurium phage type DT104 has become an important emerging pathogen. Isolates of this phage type often possess resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT resistance). The mechanism by which DT104 has accumulated resistance genes is of interest, since these genes interfere with treatment of DT104 infections and might be horizontally transferred to other bacteria, even to unrelated organisms. Previously, several laboratories have shown that the antibiotic resistance genes of DT104 are chromosomally encoded and involve integrons. The antibiotic resistance genes conferring the ACSSuT-resistant phenotype have been cloned and sequenced. These genes are grouped within two district integrons and intervening plasmid-derived sequences. This sequence is potentially useful for detection of multiresistant DT104.
Oxytetracycline-resistant (OTr) mesophilic aeromonads were recovered from untreated hospital effluent (72 isolates) and from fish farm hatchery tanks (91
isolates) at sites within the English Lake District, Cumbria, England. The transfer of OTr plasmids from these isolates was investigated. Using Escherichia coli J53-1 as a recipient, 11 isolates from the hospital site and 6 isolates from the fish farm site transferred OTr plasmids (designated pFBAOT1 to 17). Original isolates were identified using fatty acid methyl ester and fluorescent amplified
fragment length polymorphism comparisons as either Aeromonas hydrophila HG3 (eight isolates), A. veronii b.v. sobria HG8 (six isolates), and A. caviae HGB5 (one isolate). One isolate remained unidentified, and one could not be assigned a taxonomic designation beyond the genus
level. Plasmids pFBAOT1 to -17 were screened for the presence of the tetracycline resistance determinants Tet A to E and Tet
G. Only determinant Tet A (10 plasmids) was detected in these plasmids, with 7 tet gene determinants remaining unclassified. In all cases, Tet A was located on a 5.5-kbEcoRI restriction fragment. Hybridization withinc-rep probes N, P, Q, W, and U showed pFBAOT3, -4, -5, -6, -7, -9, and -11, from the hospital environment, to be IncU plasmids.
Further, restriction fragment length polymorphism (RFLP) analyses and DNA probing demonstrated that pFBAOT plasmids were closely
related to IncU OTr plasmids pASOT, pASOT2, pASOT3, pRAS1 (originally isolated from A. salmonicida strains from fish farms in Scotland and Norway, respectively), and pIE420 (isolated from a German hospital E. coli strain). In addition, DNA analyses demonstrated that plasmids pRAS1 and pIE420 had identical RFLP profiles and that all fragments
hybridized to each other. The presence of tetracycline resistance transposon Tn1721 in its entirety or in a truncated form in these plasmids was demonstrated. These results provided direct evidence that related
tetracycline resistance-encoding plasmids have disseminated between differentAeromonas species and E. coli and between the human and aquaculture environments in distinct geographical locations. Collectively, these findings provide
evidence to support the hypothesis that the aquaculture and human compartments of the environment behave as a single interactive
compartment.
Surveillance of bacterial susceptibility to five antimicrobial agents was performed during a 1-year period in and around four
freshwater fish farms situated along a stream in western Denmark. Besides assessing the levels of antibiotic resistance among
the culturable fraction of microorganisms in fish, water, and sediment samples, two major fish pathogens (88Flavobacterium psychrophilum isolates and 134Yersinia ruckeri isolates) and 313 motileAeromonas isolates, representing a group of ubiquitous aquatic bacteria, were isolated from the same samples. MICs were obtained applying
a standardized agar dilution method. A markedly decreased susceptibility of F. psychrophilum isolates to most antimicrobial agents presently available for use in Danish aquaculture was detected, while the collected
Y. ruckeriisolates remained largely sensitive to all therapeutic substances. Comparing the inlet and outlet samples, the increase of
the antibiotic-resistant proportions observed among the culturable microflora was more pronounced and statistically significant
among the motile aeromonads. High levels of individual and multiple antimicrobial resistances were demonstrated within the
collected flavobacteria and aeromonads, thus indicating a substantial impact of fish farming on several groups of bacteria
associated with aquacultural environments.
This study describes the characterization of the recently describedSalmonella genomic island 1 (SGI1) (D. A. Boyd, G. A. Peters, L.-K. Ng, and M. R. Mulvey, FEMS Microbiol. Lett. 189:285–291, 2000),
which harbors the genes associated with the ACSSuT phenotype in a Canadian isolate of Salmonella enterica serovar Typhimurium DT104. A 43-kb region has been completely sequenced and found to contain 44 predicted open reading frames
(ORFs) which comprised ∼87% of the total sequence. Fifteen ORFs did not show any significant homology to known gene sequences.
A number of ORFs show significant homology to plasmid-related genes, suggesting, at least in part, a plasmid origin for the
SGI1, although some with homology to phage-related genes were identified. The SGI1 was identified in a number of multidrug-resistant
DT120 and S. enterica serovar Agona strains with similar antibiotic-resistant phenotypes. The G+C content suggests a potential mosaic structure
for the SGI1. Emergence of the SGI1 in serovar Agona strains is discussed.
We have so far mainly examined mechanisms and processes that control populational, community, and ecosystem changes over relatively short time periods (up to a year) and relatively small spatial scales. Marine systems are also exposed to changes at rather larger scales and over multiyear (secular) time intervals. Different processes and mechanisms may be involved in changes over different ranges space and time intervals.
The concentrations of oxytetracycline and the frequencies of oxytetracycline resistant microorganisms were determined in 11 samples taken from the sediments in the vicinity of a block of fish cages at a marine salmon farm. The cage block contained 10 tonnes of Atlantic salmon smolts and a total of 20 kg of oxytetracycline were administered during the 12 day treatment. Samples cores were collected by divers 5 days after the end of the period of therapy and the top 2 cm of each core was analysed. HPLC analysis was able to quantify the oxytetracycline concentrations in three of the six samples taken directly under the cage block. The mean concentration under the cage was between 0.65 and 1.2 μg g⁻¹ (n = 6) depending on the values attributed to samples where the concentrations were below the level of quantitation (1.2 μg g⁻¹). In the five samples taken from locations not directly under the cage block oxytetracycline was only detected in the sample taken adjacent to, and down current from, the cage block. This sample was collected 10 m to the west of the cage block and contained 4.2 μg g⁻¹ oxytetracycline. These data indicate that oxytetracycline was confined to an area of the sediment which was smaller in extent than the area of the cage block itself.
Stress in fish caused by physical disturbances encountered in aquaculture, such as handling and transport, evokes a variety of responses that may be adaptive or maladaptive. The overall effect of stress may be considered as a change in biological condition beyond the normal resting state that challenges homeostasis and, thus, presents a threat to the fish's health. These stress-induced changes are grouped as primary; secondary, which includes metabolic, hematological, hydromineral, and structural; and tertiary or ‘whole animal’ responses. Many of these responses can be used as quantitative indicators of stress although investigators need to be aware of the various ‘nonstress’ factors that can also influence these conditions. A major focus of current research is on the response of the hypothalamic-pituitary-interrenal axis and the resultant elevation of circulating corticosteroids. Stress, through the action of corticosteroids, may (a) reduce immunocompetence by influencing lymphocyte numbers and antibody-production capacity, and (b) affect reproduction by altering levels and patterns of reproductive hormones that influence maturation. Stress may also alter metabolic scope in fish and affect growth, partly as a result of the catabolic or gluconeogenic effect of corticosteroids. Although certain stressors encountered during normal aquacultural procedures may be unavoidable, a number of practical approaches are suggested that would help to alleviate the detrimental effects of stress in fish.
The depletion of many marine fisheries has created a new impetus to expand seafood production through fish farming, or aquaculture. Marine aquaculture, especially of salmon and shrimp, has grown considerably in the past two decades, and aquaculturists are also beginning to farm other marine species. Production data for salmon and shrimp indicate that farming supplements, rather than substitutes for fishing. Since most farmed marine fish are carnivores, farming them relies on the capture of finite supplies of wild fish for use in fish feeds. As aquaculture is not substituting for wild fisheries, heavy dependence on wild fish inputs is a concern as marine aquaculture grows. Other likely impacts include escapes of farmed fish and large-scale waste discharges from fish farms. A viable future for marine ecosystems will require incorporation of ecological perspectives into polices that integrate fishing, aquaculture, and conservation.
Oxytetracycline, oxolinic acid, and flumequine are at present the most frequently used antibacterial agents in the treatment of marine farmed fish in Norway. These substances are supplied with the food pellets and a substantial amount ends up in the sediment under the net pens. The effects of these antibacterial agents on the microbial community in a sediment were experimentally examined in tanks containing sediment to which was added either oxytetracycline, oxolinic acid, or flumequine, and supplied with a constant water flow. During the first 20 days of the experiment, approximately one-third of the antibacterial agents disappeared from the sediments. During the next 165 days another 25% vanished. There were elevated numbers of bacteria resistant to oxytetracycline and oxolinic acid a few days after the start of the experiment. The resistance that developed to oxytetracycline was higher and longer lasting than that to oxolinic acid and flumequine. Of the quinolones, flumequine seemed least disposed to induce resistance. The number of bacteria in all treated sediments decreased to 50–67% of the numbers in the control sediment 2 days after medication. Seven days after medication the sulfate reduction rates in the treated sediments were reduced to less than 10% of the rates found in the control. This effect lasted at least 29 days, but after 70 days the inhibition of the sulfate reduction in the treated sediments had disappeared. Key words: antibacterial agents, sediment, bacterial resistance, sulfate reduction.
As aquaculture has developed, a range of bacterial diseases have been encountered that have caused both major production problems and animal welfare difficulties. These diseases were initially controlled almost exclusively by the use of antimicrobial agents. Fish farming is now a sufficiently large and mature an industry to have justified the development of an effective range of vaccines that have largely supplanted the use of antimicrobial agents for most bacterial diseases in salmonid farming in Europe and North America. For most salmonid bacterial diseases, use of antimicrobial agents is now largely confined to emergency use in the event of breakdown of vaccine protection. In addition to the increasing availability of vaccines, aquaculture is steadily developing a range of improved husbandry methods to reduce the impact of disease. Although there is evidence that antibiotic resistance can be selected for in normal therapeutic use in aquaculture, the risks of transfer of such resistance to human consumers by any of the possible routes appears to be low. Where new species are under development for aquaculture and during the development of these species, bacterial diseases may be expected to occur that will need use of antimicrobials for disease control before vaccines can be developed. If antimicrobials were not available for use with new species, development would be likely to transfer to countries with poorer controls on antibiotic use. Use of antimicrobial agents in ornamental fish, particularly in some exporting countries, is significant, and evidence exists that multiple antibiotic resistant bacteria may be frequent in such animals. Although ornamental fish are not eaten, they do enter homes and are in close contact with humans.
On 15 occasions, during and after a therapeutic treatment of fish in an Atlantic salmon farm, oxytetracycline concentrations were determined in samples of blue mussels collected at two sites in the vicinity of the farm. Oxytetracycline was not detected in any samples of mussels collected 20 m from the cage block at a depth of 1 m. Those mussels sampled from immediately under one cage (Cage 65) at the farm (10–11 m depth) contained a concentration of 10.2 μg oxytetracycline g−1 of soft tissue on the last day of treatment. After the end of oxytetracycline administration the concentration detected in these samples declined exponentially (r2 = 0.94) with a half-life of approximately 2 days.At the time of the treatment the farm was stocked with 144 tonnes of fish and 186 kg of oxytetracycline were administered during a ten day treatment. In muscle samples taken from fish (n = 5) in Cage 65, after 8 days of therapy the mean oxytetracycline concentration was 1.3 ± 0.9 μg g−1. Three days after the end of the therapy the top 2 cm of the sediments beneath Cage 65 contained 9.9 ± 2.9 μg g−1 (n = 5). These tissue and sediment concentrations lie within the ranges of values that have previously been reported for such treatments.It is argued that residues present in filter feeding bivalves that occur as a consequence of the therapeutic use of oxytetracycline in marine fish farms are unlikely to present a significant human health hazard.
The rapid expansion of the salmon aquaculture industry in the last decade and the intentional and unintentional use of many
chemicals have resulted in wastes that may have a direct environmental impact. Thus, methods and criteria are required to
assess the environmental impact of these chemicals, in particular to identify the hazards and assess the risks of their uses.
We describe a project in progress that is aimed at identifying the source of chemical wastes of salmon aquaculture in the
Bay of Fundy, the quantities released, their distribution, and environmental fate. The project is also concerned with the
effects of chemical wastes on important fisheries resources. Laboratory studies indicated that chemicals used in the treatment
of sea-lice infestations are lethal to shrimp and lobsters. Lobsters exposed to sublethal concentrations of one of these chemicals,
azamethipohos, had decreased reproductive success compared to control lobsters. However, more information is required to estimate
the associated risk to wild populations of lobster and shrimp.
Applying high-performance liquid chromatography (HPLC) and microbiological assays, various antibacterial agents were tested for their stability in an artificial marine aquaculture sediment under laboratory conditions. HPLC analysis revealed that oxolinic acid (OXA), flumequine (FLU), oxytetracycline (OTC) and sulfadiazine (SUL) were stable, while sulfadimethoxine (SMX) decreased by ca. 20% during the experimental period of 180 days. Ormethoprim (OMP) and trimethoprim (TMP) were unstable and could not be detected after 1 and 2 months, respectively. Microbiological test-systems measured no decrease in the antimicrobial activity of sediments to which OXA, FLU, SUL and SMX were added. In the OTC- and OMP-treated sediments, no antibacterial activity was found 1 month after addition of the antibacterial agents. Two months following administration the antibacterial activity in the TMP-treated sediment was considerably reduced and after 3 months no antibacterial activity could be observed.
The use of oxytetracycline for preventing and controlling bacterial pathogens in salmon farming is frequent in Chile, yet no studies have been performed to evaluate the ecological impact of its intensive and prolonged use. In this work, the frequency of oxytetracycline-resistant bacteria from water, pelletized feed and fingerlings from four Chilean freshwater Atlantic salmon farms, as well as the level of resistance of selected strains was investigated. Viable bacterial counts were performed by a spread plate method and antibiotic-resistant bacteria were counted in culture media supplemented with the selected antibiotic. Resistance levels of selected strains isolated in media containing antibiotic were determined using an agar plate dilution method. High proportions of low- and high-level oxytetracycline-resistant bacteria (selected in agar plates containing 30 and 100 μg/ml, respectively), mainly from pelletized feed and effluent samples of the fish farms were found. The highest proportions of resistant bacteria were found in the effluent samples, and were significantly higher (P<0.05, Tukey's test) than those from the other samples studied. On the contrary, influent samples exhibited the lowest proportions of resistant bacteria. One hundred and three resistant Gram-negative isolates, which represented the oxytetracycline-resistant bacterial population, were randomly selected on TSA containing 30 or 100 μg/ml of oxytetracycline, from salmon farms and pellet samples, and streaked for purification on TSA plates without oxytetracycline. A large number of non-fermenting bacteria (77.7%) were identified. Among these, Pseudomonas fluorescens (28.2%), Stenotrophomonas maltophilia (5.8%), Sphingomonas paucimobilis (5.8%), Acinetobacter lwoffii (4.8%), and Pseudomonas putida (4.8%) were the most frequent. Also, an important number of strains of Aeromonas hydrophila (9.7%), Burkholderia cepacia (3.9%), Brevundimonas vesicularis (3.9%), Acinetobacter johnsonii (2.9%), Pantoea sp. (2.9%) and Moraxella sp. (2.9%) were found. P. fluorescens and A. hydrophila predominated in salmon fingerlings, whereas A. lwoffii and S. maltophilia were predominant in pellet samples. Selected strains exhibited high levels of oxytetracycline resistance, with minimum inhibitory concentrations (MICs) ranging from 64 to 2048 μg/ml, whereas MIC90 of oxytetracycline varied between 1024 and 2048 μg/ml. This study shows the presence of an important population of oxytetracycline-resistant bacteria in the microflora of Chilean salmon farms. Therefore, the environment of these farms might play important roles as reservoirs of bacteria carrying genetic determinants for high-level tetracycline resistance, prompting an important risk to public health for workers involved in fish culturing and processing.
Acinetobacter spp. were used as bacterial indicators to monitor antimicrobial resistance in a freshwater trout farm before and after treatment with oxolinic acid (OA)-medicated feed. The level of susceptibility to four antimicrobial agents was determined in 331 Acinetobacter isolates obtained by a selective procedure from a pond (n=100), the inlet channel (n=105), and the stream receiving the farm effluent (n=126). Before treatment, OA resistance was detected only among isolates from the pond (40%), in which the last medication with OA was dated back to 6 months before. Following treatment, a high prevalence of OA resistance was observed among isolates from both the pond (33–53%) and the effluent recipient (21–55%). In contrast, no OA resistant strains were isolated from the inlet channel. OA resistant strains were significantly more resistant to oxytetracycline (OT) compared with OA sensitive strains (P<0.0001, odds ratio=43.6). Furthermore, OA resistant isolates showed an increase of at least 10-fold times in the MIC values for ciprofloxacin (CIP) resistance compared with sensitive isolates. Phenotypic characterisation and PCR-based fingerprinting analysis showed lower diversity among Acinetobacter isolates from the pond and the stream receiving the farm effluent in comparison with isolates from the inlet channel. Since the two biotypes predominant in the pond and the effluent recipient included the vast majority of OA resistant isolates, the low diversity of Acinetobacter spp. observed at these sites could have been enhanced by exposure to the drug. The results of this study indicate that the use of OA in inland farms can affect the levels of antimicrobial resistance and diversity in the microflora of natural aquatic habitats situated downstream. Since the ecological consequences deriving from changes of the indigenous aquatic microflora are unknown, the careful consideration of the use of OA in aquaculture was suggested.
The persistence of the antibacterial agents oxytetracycline chloride (OTC), oxolinic acid (OA), flumequine (FLU), sarafloxacin (SAR), florfenicol (FLO), sulfadiazine (SDZ) and trimethoprim (TRM) were compared in marine sediments. Polyethylene boxes were filled with sediment, the antibacterial compounds added and placed on the sea bed at approximately 15 m depth for a period of 180–230 days. Sediment cores were collected by a diver and analyzed for residues of the antibacterials in four depth intervals from 1 to 7 cm. OTC and the quinolones OA, F and SAR were found to be very persistent in the sediment. In the deeper layer of the sediment the initial concentrations of these compounds were present after 180 days, whereas the residues in the top layer of the sediment depurated more rapidly. The depuration of these substances from the sediment is most probably due to leaching and redistribution rather than degradation. The quinolones were found to adsorb to sediment. SDZ and TRM were less persistent than the quinolones; however, the estimated half-life in the deepest layer (6–7 cm) was approximately 90 days for both substances. The concentration of FLO decreased rapidly in the sediment with a calculated half-life of 4.5 days, and a metabolite, florfenicol amine, was identified in the sediment.
Injudicious use of the fluoroquinolones may result in treatment failure, increased patient morbidity, increased health care cost, and possible patient fatality. Fluoroquinolone-resistant bacteria may also adversely impact the microbiological environment in the hospital, the local community and eventually large geographical regions. Fluoroquinolone resistance develops in a stepwise fashion, and current susceptibility testing methods and recommended MIC susceptible breakpoint values for the United States may fail to identify some bacteria that are resistant due to first step mutations at the fluoroquinolone target site gene sequences. C-8 methoxy- fluoroquinolone compounds are more active against resistant bacteria than the older compounds. Fluoroquinolone resistance relates directly to human and veterinary usage and emerging bacterial resistance poses the single greatest threat to the future survival of the fluoroquinolone drugs as an antibiotic class.
In 1969 and 1970, Salmonella agonaemerged as a public-health problem in the U.S.A., the U.K., Netherlands, and Israel. In each country an initial isolation from Peruvian fishmeal was followed by recovery of S. agona from domestic animals and subsequently from man. By 1972, S. agona was the 8th most commonly isolated serotype in the U.S.A., accounting for more than 500 cases in man, and the 2nd most common serotype in the U.K., causing approximately 700 cases. A detailed investigation of an outbreak in Paragould, Arkansas, traced the source of infection from a local restaurant back to a Mississippi poultry farm using Peruvian fishmeal. This outbreak illustrates the complexity of the chain of transmission of salmonellosis and emphasises the importance of animal feeds in salmonellosis in man.
An MIC test of 12 chemotherapeutic agents performed on 175 strains of Pasteurella piscicida collected from cultured yellowtail (Seriola quinqueradiata) in different areas of Japan from 1989 to 1991 revealed 152 strains (87%) with resistance to combinations of ampicillin (AP), chloramphenicol (CP), kanamycin (KM), nalidixic acid (NA), sulfamonomethoxine (SA), tetracycline (TC), and/or trimethoprim (TMP). The remaining 23 strains were sensitive to all the drugs tested: AP, cefazolin, CP, florfenicol (FF), furazolidone, KM, NA, novobiocin, SA, streptomycin, TC, and TMP. FF showed the most effective antibacterial activity against P. piscicida with MICs ranging from 0.004 to 0.6 microgram/ml. One hundred and forty-nine of the 152 resistant strains carried transferable R plasmids encoding one of the Cp Km Sa Tc, Km Sa Tc, Km Sa, and Sa resistance. The most common resistance marker of transferable R plasmids identified in P. piscicida was Km Sa Tc. R plasmids encoding three different resistant markers were very similar on the basis of their digestion patterns with restriction endonucleases. There was homology among the DNAs of nine transferable R plasmids selected. Our findings suggest that multiple drug resistant strains of P. piscicida carrying transferable R plasmids with the same DNA structure are common in yellowtail farms and that the R plasmid has been retained within the P. piscicida population without change in their DNA structure according to geography and year.
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