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Evidence of Direct Transmission of Escherichia coli 0157:H7 Infection between Calves and a Human
... Gram + bacillus III Anthrax Worldwide Cinquetti et al. 2009, Doganay et al. 2010, International Society for Infectious Diseases 2007a, 2010a, 2011b, 2011c, 2011d, 2012a, 2012b, 2012k, Kim et al. 2001, Leblebicoglu et al. 2006, Lester et al. 1997, Schwartz et al. 2002 2007d, 2007e, 2007f, 2008d, 2009b, 2009c, 2010d, 2010e, 2010f, 2011f, 2012c Clostridium difficile 1998, 2005a, 2005b, 2006a, 2006b, 2006c, 2007g, 2010g, 2012g, 2012h, Parry et al. 1995, Renwick et al. 1993 Baxby et al. 1994, Bhanuprakash et al. 2010, Essbauer et al. 2010, International Society for Infectious Diseases 2007k, 2011g, Megid et al. 2008, Nitsche et al. 2007, Pelkonen et al. 2003, Schnurrenberger et al. 1980, Schupp et al. 2001, Singh et al. 2007, Trindade et al. 2009, Wienecke et al. 2000, de Souza Trindade et al. 2007 Wesselsbron Nowgesic et al. 1999, Tacket et al. 1984 Biothreat category based on the CDC classification (Centers for Disease Control and Prevention 2011a); Emerging/Reemerging status based on the NIAID classification (National Institute of Allergy and Infectious Diseases 2011). (Moda et al. 1996). ...
... Gastrointestinal infections are among the most common cattle zoonoses, in part because of their ubiquitous nature (Tables 2 and 3). Outbreaks involving contaminated cattle products have been well documented for a number of bacterial species, including enterohemorrhagic Escherichia coli (Renwick et al. 1993, Parry et al. 1995 2012j). While local laws have been adopted in some areas in an effort to prevent such outbreaks, many people in both the United States and around the world preferentially consume these products. ...
... Our review of the literature revealed a number of unusual cases of nonfoodborne zoonotic transmission of B. anthracis (Centers for Disease Control and Prevention 2010), Campylobacter spp. (Gilpin et al. 2008), E. coli (Renwick et al. 1993, Parry et al. 1995, Waguri et al. 2007, and Salmonella spp. (Hendriksen et al. 2004, Bemis et al. 2007) that resulted in gastrointestinal illness in humans. ...
Abstract Infectious disease prevention and control has been among the top public health objectives during the last century. However, controlling disease due to pathogens that move between animals and humans has been challenging. Such zoonotic pathogens have been responsible for the majority of new human disease threats and a number of recent international epidemics. Currently, our surveillance systems often lack the ability to monitor the human-animal interface for emergent pathogens. Identifying and ultimately addressing emergent cross-species infections will require a "One Health" approach in which resources from public veterinary, environmental, and human health function as part of an integrative system. Here we review the epidemiology of bovine zoonoses from a public health perspective.
... Serotypes in bold have been isolated previously from humans, and those in bold and underlined have been associated previously with bloody diarrhea or hemolytic uremic syndrome [1,[7][8][9][10][11]. LPS in family members. Transmission of VTEC from cattle to people in this setting is not surprising, since dairy farm families are exposed directly to cattle manure and many consume raw milk, both known risk factors for human VTEC infection [34,35]. Although exposure to cattle or manure was not identified as a risk factor for VTEC infection in this study, VTEC are probably widespread in the farm environment, making differences in environmental exposure difficult to detect by the study methods used. ...
... Initial immunizing infections of farm residents may cause uncomplicated diarrhea, since many VTEC isolated from cattle belong to serotypes associated with this form of VTEC-related human illness [1,7]. More serious disease may occur where susceptible farm residents are exposed to E. coli 0157:H7 present in cattle on the farm [35]. ...
... Exposure to the dairy farm environment may have greater health significance for urban residents and specific subgroups within the rural community. Urban residents who visit farms, have direct contact with cattle [35,37], or consume unpasteurized milk [15,23] may be expected to have a higher risk of VTEC infection and disease due to less prior exposure to VTEC. In addition, children with declining maternal immunity, the elderly, and other immunocompromised individuals who live on dairy farms may have increased risk of infection and VTEC-associated disease. ...
Fecal samples from 335 dairy farm residents and 1458 cattle on 80 farms were tested for Vero cytotoxin (VT)–producing Escherichia coli (VTEC). Residents were also tested for antibodies to VT1 and O157 lipopolysaccharide (LPS). Residents and cattle on farms
with VTEC-positive persons or E. coli O157:H7–positive cattle were retested. Twenty-one persons (6.3%) on 16 farms (20.8%) and 46% of cattle on 100%of the farms
had VTEC in fecal samples. Human VTEC isolates included E. coli O157:H7 and 8 other serotypes, 4 of which were present in cattle on the same farms. More persons had antibodies to VT1 (41%)
than to O157 LPS (12.5%). Seropositivity to 0157 LPS was associated with isolation of E. coli O157:H7 on the farm (P = .022). Human VTEC infection was negatively associated with age (P < .05) and was not associated with clinical illness. Many dairy farm residents experience subclinical immunizing VTEC infections
at a young age, which frequently involve non-O157 VTEC found in cattle.
... Introduction E stimated to cause over 63,000 foodborne illnesses annually, Escherichia coli O157:H7 represents a significant public health threat (Mead et al., 1999;Scallan et al., 2011). Cattle are recognized as the principal reservoir for Escherichia coli O157:H7 (Chapman et al., 1993;Hancock et al., 1997;McDaniel et al., 2014;Renwick et al., 1993;Whipp et al., 1994) and asymptomatic carriers, with studies showing up to 30% of cattle harboring the pathogen (Callaway et al., 2009;Callaway et al., 2006;Reinstein et al., 2007;Stanford et al., 2005). The U.S. Food and Drug Administration, Centers for Disease Control and Prevention, and Department of Agriculture surveyed foodborne illness data from 1998 to 2017 and determined that 25.8% of foodborne Escherichia coli O157:H7 illnesses were attributable to beef (Interagency Food Safety Analytics Collaboration, 2019). ...
Cattle are recognized as the principal reservoir for Escherichia coli O157:H7 and preharvest food safety efforts often focus on decreasing shedding of this pathogen in cattle feces. Enogen® corn (EC; Syngenta Seeds, LLC) is genetically modified to produce enhanced concentrations of α-amylase in the corn kernel endosperm. Research has demonstrated improvements in feed efficiency for cattle fed EC and research has not yet explored whether improved digestion impacts foodborne pathogen populations in cattle. Therefore, this study explored effects of finishing diets containing EC on Escherichia coli O157:H7 prevalence in cattle. A 2 × 2 factorial experiment was conducted with steers (n = 960) fed diets consisting of 2 types of silage (EC or Control) and grain (EC or Control), fed daily ad libitum. Steers were grouped into 12 blocks by incoming body weight, blocks were randomly assigned to one of four pens, and pens were randomly assigned to one diet. Cattle were sampled using rectoanal mucosal swabs in cohorts of 298-337 cattle per day, for a total of 3 sampling days (15-16 days apart). Escherichia coli O157:H7 prevalence rates ranged from not detected (0/75) to 10.0% (8/80) depending on sampling day. Tests for the silage × corn interaction, and the main effects of silage and corn, were not significant (p > 0.05); however, EC reduced the odds of Escherichia coli O157:H7 prevalence by 43% compared to the control corn diet (p = 0.07). Diets containing EC tended to decrease Escherichia coli O157:H7 prevalence in feedlot cattle; however, this reduction was not significant. Before a conclusion can be drawn about impact of EC on Escherichia coli O157:H7 in cattle, further research is necessary to (1) determine if this tendency is due to increased alpha amylase activity and (2) elucidate impact on Escherichia coli O157:H7 prevalence and concentration, as well as a possible mechanism of action.
... Consequently, gardening and visits to farms or petting zoos are also documented sources of STEC infection. The first case of STEC transmitted by animal contact was reported in 1992 (Renwick et al. 1993). STEC can be transmitted by touching the hair or hide of an infected animal (Elder et al. 2000). ...
Although Shiga toxins are produced by particular E. coli serotypes, the genes transcribed, as well as the timing and quantity of transcription, are determined by lambdoid phages (phages related to phage λ) that infect those serotypes. A lambdoid phage is referred to as temperate when it integrates into a host cell genome and replicates its DNA “lysogenically” (as the cell replicates its DNA). A stressed cell detects DNA damage and figuratively sends out an “SOS.” The phages have a sophisticated mechanism that detects the host cell SOS response to DNA damage and responds by replicating “lytically” (with lysis of the host cell). Each “Stx-phage” has one Shiga toxin operon, composed of genes encoding the Shiga toxin StxA and StxB subunits. However, an individual Stx-phage may integrate into a bacterial chromosome more than once, and different species of Stx-phage can infect a bacterium simultaneously. Both the multiplicity of infection and recombination events permit a single host to produce more than one type or variant of Shiga toxin, each produced under the control of its own phage. Additional transposable elements (transposons) from the bacterial host add to this genetic diversity, and all levels of this diversity are transmissible to other bacterial hosts. To combat phages, bacterial hosts have a primitive adaptive immune system that employs clustered, regularly-interspaced, short palindromic repeats (CRISPR) and the CRISPR-associated genes (CAS). CRISPR/CAS can inactivate infecting Stx-phages.
... 119,[122][123][124][125][126] Two main intervention strategies have been proposed: i) vaccination of the infant population; and ii) vaccination of cattle, the main animal reservoir and the primary means of human contamination, due to the consumption of poorlycooked meat. 127 It should be noted that cattle colonized by STEC are generally asymptomatic, thus subsidies for farmers may be necessary to promote animal vaccination. Hurd and Malladi 122 predicted a 60% decrease in human cases associated with O157:H7 assuming a bovine vaccination effectiveness of 80% and an adoption rate of 100%. ...
In Part II we discuss the following bacterial pathogens: Shigella, Salmonella (non-typhoidal), diarrheogenic E. coli (enterotoxigenic and enterohemorragic) and Campylobacter jejuni. In contrast to the enteric viruses and Vibrio cholerae discussed in Part I of this series, for the bacterial pathogens described here there is only one licensed vaccine, developed primarily for Vibrio cholerae and which provides moderate protection against enterotoxigenic E. coli (ETEC) (Dukoral→), as well as a few additional candidates in advanced stages of development for ETEC and one candidate for Shigella spp. Numerous vaccine candidates in earlier stages of development are discussed.
... Three incidents of apparent direct transmission of E. coli O157:H7 from bovines to humans have been reported (Renwick et al. 1993;Synge et al. 1993;Rice et al. 1996). In Ontario, Canada, in 1992, a 13-mo-old boy was hospitalized with hemorrhagic colitis following prolonged contact with calves on a dairy farm. ...
Escherichia coli 157:H7 has evolved as an important foodborne pathogen since its initial description in 1982. Outbreaks of illness associated with E. coli O157:H7 have been reported throughout the northern hemisphere, most frequently in Canada, the United States, Japan, and the United Kingdom. In Canada, infections due to E. coli O157:H7 appear to be more Common in the western provinces than in the east, in rural vs. urban environments, and during summer as opposed to winter months. Undercooked ground beef has been implicated as the primary vehicle in E. coli O157:H7 infection, but contaminated fruits, vegetables and water have also been linked to E. coli O157:H7 outbreaks. Epidemiological investigations demonstrate that dairy and beef cattle are primary reservoirs of this organism, carrying it asymptomatically and shedding it intermittently and seasonally in their feces. Surveys in Canada and the United States indicate widespread distribution of E. coli O157:H7 in cattle operations. The prevalence of E. coli O157:H7 in cattle has been increasing in recent reports, likely due to the development of more sensitive methods for the detection of the organism. Escherichia coli O157:H7 has been isolated from feed, water for livestock, manure, soil and flies, all of which represent potential sources of contamination for cattle and their environment. To date, effective methods for controlling E. coli O157:H7 in cattle have not been identified, although dietary manipulation, vaccination and bacteriophage therapy have been reported to have potential as intervention strategies. Effective control of E. coli O157:H7 requires reducing the frequency and intensity of fecal shedding of this pathogen by cattle, in addition to targeting environmental sources of the organism.
... Unlike the detection of other intestinal pathogens which are identified by standard routine stool examination, the diagnosis of E.coli O157: H7 requires the detection of toxins as well as the bacteria itself 10 . The presence of shiga-like toxin can be detected by demonstrating cytotoxicity, dot-blotting, Polymerase Chain Reaction or by ELISA [10][11][12][13][14][15][16] . ...
Objectives: The first cases of E.coli O157: H7 infection in Iraq are reported in order to determine their association with Hemolytic Uremic syndrome (HUS). Design: Methods: Blood, urine, and stool samples were collected from 687 hospitalized children with diarrhoea in Basrah, Iraq. The causative agents (Bacteria and parasites) for diarrhoea were identified, especially E.coli O157: H7 which was subjected to serotyping by fluorescent technique. Direct smear; Ritchie formalin– ether–sedimentation concentration and modified Ziehl-Neelsen staining techniques were used to identify the parasitic infections in stool samples. General urine analysis and complete blood picture were studied as well. Results: Eighteen (2.6%) children were found to-be infected with E.coli O157: H7, half of them (50%) developed HUS. The infection rate was higher among infant boys residing in rural areas. The duration of illness ranged from 2-14 days, with mild clinical presentation and was distinguished from other bloody diarrheal infections by the lack of fever. Receiving antimicrobial therapy has no meaningful effect in reducing the complication of HUS. Conclusion: The present study provided useful information on the seasonal occurrence, age at risk, pattern of feeding among children<2 year of age and highlighting the importance of one of emerging infectious agents in Iraq.
... However, over the last 2 decades a wide variety of food items have been linked with disease due to E. coli O157:H7 infection, such as unpasteurized fruit juices (5), smoked meats (6), and fresh produce (7)(8)(9)(10). Moreover, other routes of STEC transmission that are unrelated to ingestion of contaminated foods have been identified, and these include swimming in contaminated water (11)(12)(13), contact with infected animals (14,15), and person-to-person spread (16,17). These modes of transmission are likely facilitated by the fact that E. coli O157:H7 can cause illness after exposure to Ͻ100 organisms (4). ...
Shiga toxin (Stx)-producing Escherichia coli (STEC) causes hemorrhagic colitis and the hemolytic-uremic syndrome (HUS). STEC strains may produce Stx1a and/or Stx2a or
variants of either toxin. A 2006 spinach-associated outbreak of STEC O157:H7 resulted in higher hospitalization and HUS rates
than previous STEC outbreaks. The spinach isolate, strain K3995, contains both stx2a and stx2c. We hypothesized that the enhanced virulence of K3995 reflects the combination of stx2 alleles (carried on lysogenic phages) and/or the amount of Stx2 made by that strain. We compared the virulence of K3995 to
those of other O157:H7 isolates and an isogenic Stx2 mutant in rabbits and mice. We also measured the relative levels of Stx2
produced from those strains with or without induction of the stx-carrying phage. Some rabbits infected with K3995 exhibited intestinal pathology and succumbed to infection, while none of
those infected with O157:H7 strain 2812 (Stx1a+ Stx2a+) died or showed pathological signs. Rabbits infected with the isogenic Stx2a mutant K3995 stx2a::cat were not colonized as well as those infected with K3995 and exhibited no signs of disease. In the streptomycin-treated mouse
model, more animals infected with K3995 died than did those infected with O157:H7 strain 86-24 (Stx2a+). Additionally, K3995 produced higher levels of total Stx2 and toxin phage DNA in cultures after phage induction than did
86-24. Our results demonstrate the greater virulence of K3995 compared to other O157:H7 strains in rabbits and mice. We conclude
that this enhanced virulence is linked to higher levels of Stx2 expression as a consequence of increased phage induction.
... Gårdsbesøk kan utgjøre risiko for smitte, da bakterien kan forekomme i alt fra gjødselhauger til fòr og gårdsredskaper (Johnson et al., 1999). Renwick et al. fant i 1993 bevis for direkte overføring av E. coli O157:H7 fra kalv til menneske. En 13 måneder gammel gutt ble syk etter å ha lekt med kalver i et fjøs. ...
... There have been reported cases of human E. coli O157 infection through the direct ingestion of contaminated faecal material (Renwick et al., 1993 ). Laboratory studies on the persistence of E. coli O157 in inoculated, non-aerated, progressively drying cattle faeces has shown a transient increase (1 to 7 d) in population followed by a gradual decline until the pathogen becomes undetectable after 7 weeks (`10 cfu g 71 ; Kudva et al., 1998). ...
Escherichia coli serotype O157 is a virulent human pathogen the global incidence of which has increased. It has been demonstrated that cattle are the primary reservoir of this pathogen. This has serious implications for the land-based disposal of organic wastes such as cattle manure, cattle slurry and abattoir waste. Further, it also has serious ramifications for the protection of surface and groundwater drinking supplies and public access to pasture land. However, while soil and vegetation can be expected to directly influence the survival of this pathogen, there is a paucity of information concerning the behaviour and survival of E. coli O157 in agricultural environments. It appears that E. coli O157 presently contaminates between 1 to 15% of UK cattle herds, depending on region, and that faecal excretion of the bacterium shows a distinct seasonality which also reflects the incidence of human infections. E. coli O157 can remain viable in soil for greater than 4 months and appears to be a highly resilient pathogen possessing the capability to adapt easily to environmental stresses. While most human cases of E. coli O157 related food poisoning have been associated with the consumption of contaminated meat and dairy products, there is also evidence that human infection has occurred through the ingestion of contaminated soil, fruit and vegetables and drinking water. In this review the potential threat to human health posed by the application of contaminated organic wastes to soil and possible strategies for reducing the amount of pathogen entering the food chain are highlighted.
... Cattle and sheep are the main reservoirs of E. coli O157 (Hancock et al. 1998; Paiba et al. 2003; Synge et al. 2003). Faecal excretion of E. coli O157 may cause infection in humans due to direct contact with these animals or contact with food or water contaminated with their faeces during slaughter or grazing, respectively (Renwick et al. 1993; Armstrong et al. 1996 Therefore, cattle play an important role in the epidemiology of E. coli O157. ...
To study the occurrence and spatial distribution of Shiga toxin-producing Escherichia coli (STEC) O157 in calves less than 1-week-old (bobby calves) born on dairy farms in the North Island of New Zealand, and to determine the association of concentration of IgG in serum, carcass weight, gender and breed with occurrence of E. coli O157 in these calves.
In total, 309 recto-anal mucosal swabs and blood samples were collected from bobby calves at two slaughter plants in the North Island of New Zealand. The address of the farm, tag number, carcass weight, gender and breed of the sampled animals were recorded. Swabs were tested for the presence of E. coli O157 using real time PCR (RT-PCR). All the farms were mapped geographically to determine the spatial distribution of farms positive for E. coli O157. K function analysis was used to test for clustering of these farms. Multiplex PCR was used for the detection of Shiga toxin 1 (stx1), Shiga toxin 2 (stx2), E. coli attaching and effacing (eae) and Enterohaemolysin (ehxA) genes in E. coli O157 isolates. Genotypes of isolates from this study (n = 10) along with human (n = 18) and bovine isolates (n = 4) obtained elsewhere were determined using bacteriophage insertion typing for stx encoding.
Of the 309 samples, 55 (17.7%) were positive for E. coli O157 by RT-PCR and originated from 47/197 (23.8%) farms. E. coli O157 was isolated from 10 samples of which seven isolates were positive for stx2, eae and ehxA genes and the other three isolates were positive for stx1, stx2, eae and ehxA. Bacteriophage insertion typing for stx encoding revealed that 12/18 (67%) human and 13/14 (93%) bovine isolates belonged to genotypes 1 and 3. K function analysis showed some clustering of farms positive for E. coli O157. There was no association between concentration of IgG in serum, carcass weight and gender of the calves, and samples positive for E. coli O157, assessed using linear mixed-effects models. However, Jersey calves were less likely to be positive for E. coli O157 by RT-PCR than Friesian calves (p = 0.055).
Healthy bobby calves are an asymptomatic reservoir of E. coli O157 in New Zealand and may represent an important source of infection for humans. Carriage was not associated with concentration of IgG in serum, carcass weight or gender.
... Gårdsbesøk kan utgjøre risiko for smitte, da bakterien kan forekomme i alt fra gjødselhauger til fòr og gårdsredskaper (Johnson et al., 1999). Renwick et al. fant i 1993 bevis for direkte overføring av E. coli O157:H7 fra kalv til menneske. En 13 måneder gammel gutt ble syk etter å ha lekt med kalver i et fjøs. ...
Escherichia coli opptrer i mange varianter fra de harmløse tarmbakteriene til de svært patogene som forårsaker sykdom og død hos menneske. En har den senere tid kartlagt reservoaret til de sykdomsfremkallende variantene, og det har skjedd en rivende utvikling i forståelsen av patogenitetsmekanismene. Hensikten med denne artikkelen er å gi en oversikt over E. coli som næringsmiddeloverført patogen.
Feedlot cattle commonly shed the foodborne pathogen Escherichia coli O157:H7 in their feces. Megasphaera elsdenii (ME), a lactic acid-utilizing bacterium, is commonly administered to cattle to avoid lactate accumulation in the rumen and to control ruminal acidosis. The impact of administering ME on foodborne pathogen prevalence, specifically E. coli O157:H7, has not been explored. The purpose of this study was to quantify E. coli O157:H7 prevalence in finishing cattle administered ME. Cattle (n=448) were assigned to treatments in a randomized complete block design with repeated measurements over two sampling periods. Treatments were arranged as a 2×2 factorial containing: ruminally-protected lysine (RPL; included for a complementary study) fed at 0 or 0.45% of diet dry matter; with or without ME. Freeze-dried ME was administered as an oral drench (1x1010 CFU/steer on day one), and then top-dressed onto basal diets (1x107 CFU/steer) daily thereafter. Rectoanal mucosal swabs (RAMS) were obtained from animals before harvest to determine the E. coli O157:H7 prevalence. The inclusion of RPL (P=0.2136) and ME (P=0.5012) did not impact E. coli O157:H7 prevalence, and RPL was not included in any significant interactions (P>0.05). A significant interaction was observed between ME and sampling period (P=0.0323), indicating that the effect of ME on E. coli O157:H7 prevalence varied over sampling period. A diet containing ME reduced the odds of E. coli O157:H7 prevalence by 50% during sampling period 1 (8.0% and 14.7% for cattle with and without ME, respectively) and increased the odds by 23% during sampling period 2 (10.8% and 8.9% for cattle with and without ME, respectively). Administering ME in cattle diets did not impact E. coli O157:H7 in feedlot cattle. This is the first study to investigate the use of ME as a pre-harvest food safety intervention in cattle and additional research is necessary to determine efficacy.
Foodborne outbreaks of Shiga toxin-producing bacteria occur with disturbing regularity. The two most common Shiga toxin-producing bacteria are Shigella spp. and the Shiga toxin-producing Escherichia coli (STEC). Among foodborne pathogens, they result in a disproportionately large share of hospitalizations, serious sequelae, and deaths. In 1982 the first reported outbreak of STEC was caused by an E. coli O157:H7 serotype in undercooked hamburger, but by 2008 it was estimated that most foodborne STEC disease was caused by other serotypes. As the food service industry has adopted more stringent cooking practices and as diets have changed, the sources of outbreaks have shifted as well. The two largest outbreaks on record were caused by consumption of uncooked radish and fenugreek sprouts. There are at least 200 different known strains of STEC found in farm animals, where they can propagate “below the radar” because farm animals lack the receptors that would make them vulnerable to Shiga toxins. Future outbreaks are likely to involve other uncooked foods and different strains of STEC, and they may be triggered by the agricultural practices, food processing and transportation conditions, and ecological factors that bring them together.
It has been recognized that cattle are the main source of Escherichia coli O157:H7. This organism appears to be confined to the gastrointestinal tract and is shed in the feces. A probiotic product containing lactic acid-producing Streptococcus bovis LCB6 and Lactobacillus gallinarium LCB12 isolated from adult cattle was developed, and a preliminary experiment was conducted to evaluate its effect on the elimination of E. coli O157 from experimentally infected calves. Eight 4-month-old Holstein calves were orally challenged with E. coli O157 and the probiotic product was administered to 4 calves with continuous fecal shedding of E. coli O157 at 7 days after the infection. Fecal shedding of E. coli O157 was completely inhibited and re-shedding was not detected in any of the animals. Remarkable increase of the concentration of volatile fatty acids (VFAs), especially acetic acid in the feces after the administration of probiotic bacteria was correlated with the decrease in the number of E. coli O157. In the 4 calves in which fecal shedding of E. coli O157 had spontaneously stopped by the 7th day, a high concentration of VFAs was detected in the feces before and after the experimental infection. Although our results are preliminary and obtained from calves under limited conditions, the possibility of using a probiotic product to reduce fecal shedding of E. coli O157 from cattle was suggested.
The number of outbreaks of human illnesses caused by consumption of undercooked beef contaminated with Shiga-like toxin-producing Escherichia coli (SLTEC) such as O157:H7 has increased in recent years. As a result, cattle have been considered as reservoirs of such pathogens. The social fear and economic impact associated with this problem have prompted global research to understand the epidemiology of such pathogens with the goal to develop strategies that can be implemented at the farm and during slaughter and processing to assure beef safety. Several on-farm factors that may be manipulated to decrease the risk of sending cattle harboring SLTEC to slaughter include animal, manure handling, drinking water, feed additives, probiotics, management, feeding regime, and dietary ingredients. Several off-farm (during slaughter and processing) factors that can be improved or adapted to produce safer beef include trimming, spraying with sanitizers, hot-water washing, irradiation, using dips, and using food additives. Adaptation of several off-farm practices has been useful in removing the pathogens from beef or its products after they have been contaminated. Recently, attention has been given to those factors that can be altered before sending cattle to slaughter (e.g., on-farm). Because of the complexity of the problem, the on-farm and off-farm factors affecting beef safety should be elucidated, their roles clearly defined, and their additive impacts determined. Upon elucidation of these roles/impacts, the best pre- and post-harvest control measures can be implemented to support a competitive beef industry.
The number of outbreaks of human illnesses caused by consumption of undercooked beef contaminated with Shiga-like toxin-producing Escherichia coli (SLTEC) such as O157:H7 has increased in recent years. As a result, cattle have been considered as reservoirs of such pathogens. The social fear and economic impact associated with this problem have prompted global research to understand the epidemiology of such pathogens with the goal to develop strategies that can be implemented at the farm and during slaughter and processing to assure beef safety. Several on-farm factors that may be manipulated to decrease the risk of sending cattle harboring SLTEC to slaughter include animal, manure handling, drinking water, feed additives, probiotics, management, feeding regime, and dietary ingredients. Several off-farm (during slaughter and processing) factors that can be improved or adapted to produce safer beef include trimming, spraying with sanitizers, hot-water washing, irradiation, using dips, and using food additives. Adaptation of several off-farm practices has been useful in removing the pathogens from beef or its products after they have been contaminated. Recently, attention has been given to those factors that can be altered before sending cattle to slaughter (e.g., on-farm). Because of the complexity of the problem, the on-farm and off-farm factors affecting beef safety should be elucidated, their roles clearly defined, and their additive impacts determined. Upon elucidation of these roles/impacts, the best pre- and post-harvest control measures can be implemented to support a competitive beef industry.
The prevalence of Escherichia coli O157:H7 was investigated on samples of various portions of 190 chicken carcasses, obtained from local retail markets and poultry shops in Turkey. Immunomagnetic separation methods was used to isolate E. coli O157:H7 from the samples. Verotoxin 1 (VT1) and verotoxin 2 (VT2) productions by the isolated E. coli strains was also investigated. E. coli O157:H7 was isolated from two (1.05%) of the 190 samples of poultry meat examined. All the strains isolated produced both VT1 and VT2. These findings indicate that poultry meat can also be a source of E. coli O157:H7 infections for humans. Appropriate control measures should be developed and implemented to eliminate this human pathogen from foods of animal origin, including poultry, in order to protect human health.
To estimate the prevalence of Escherichia coli O157 on Dutch dairy herds, faecal samples were collected once from 678 randomly selected dairy farms in the period October 1996–December 2000. Samples were cultured for E. coli O157. Thirty-eight isolates were tested for virulence genes (eae, VT1 and VT2). A questionnaire about farm characteristics was taken from the farm manager, resulting in variables that could be analysed to identify and quantify factors associated with presence of E. coli O157.In total, 49 of the 678 herds (7.2%) showed at least one positive pooled sample. E. coli O157 was not isolated from herds sampled in December–April in consecutive years (except for one isolate found in March, 2000). VT- and eae-genes were found in 37 and 38 isolates, respectively. Logistic regression was performed on variables obtained from the questionnaire, comparing E. coli O157-positive herds to negative herds. To account for season, a sine function was included in the logistic regression as an offset variable. In the final model, the presence of at least one pig at the farm (OR=3.4), purchase of animals within the last 2 years before sampling (OR=1.9), supply of maize (OR=0.29) to the cows, and sampling a herd in the year 1999 or 2000 (compared to sampling in 1998; OR=2.1 and 2.9, respectively) had associations with the presence of E. coli O157.
The presence of Escherichia (E.) coli O157:H7 was investigated in raw ewes' and goats' milk samples from northern Greece. One hundred and sixteen raw milk samples originating from an equal number of different flocks were tested for the presence of E. coli O157:H7 using the standard cultural method and immunomagnetic separation. The pathogen was detected in 15 out of the 116 milk samples on the basis of biochemical and serological tests. Isolates often samples revealed the presence of the VT1 gene and the isolate of one sample showed both VT1 and VT2 genes when analyzed by polymerase chain reaction. The investigation revealed a significant incidence rate of the pathogen in unpasteurized milk used for traditional dairy products.
The contribution of RecA, Dps, and RpoS to survival of Escherichia coli O157:H7 during desiccation and osmotic stress was determined in Luria-Bertani broth with 12 % NaCl (LB-12) at 30 and 37 °C, on filter disks at 23 and 30 °C, and in sterile bovine feces at 30 °C. RecA did not significantly contribute to survival in any condition or temperature. The contribution of Dps to survival was only significant in LB-12 at 37 °C. RpoS was necessary for survival during desiccation and osmotic stress, and survival of the RpoS mutant was significantly less than the parent in all conditions and temperatures. The RpoS mutant survived up to 21 days in bovine feces, <4 days on filter disks, and >8 and <4 days in LB-12 at 30 and 37 °C, respectively. The parent, ΔrecA, dps, and dps/ΔrecA mutant strains survived >8 days in LB-12, >28 days on filter disks, and >28 days in bovine feces. Increased incubation temperatures were associated with decreased survival. E. coli O157:H7 can persist in desiccating and osmotically challenging environments, especially sterile feces, for an extended period time.
This article examines the role of nucleic acid analysis in clinical chemistry. It is a broad-based article and begins with the background knowledge which will be needed to appreciate the succeeding sections. In the Introduction, structure and function of nucleic acids, hybridization, probe labeling, hybridization protection, polymerase chain reaction (PCR) and sequencing are discussed. Major sections are devoted to microbiological analysis (with particular emphasis on bacteriology), genetic diseases and screening [discussions are provided for cystic fibrosis (CF), heriditary fructose intolerance (HFI) and hemochromatosis along with an introduction to the Human Genome Project and single nucleotide polymorphisms (SNP)], other areas of human medicine (oncology, colorectal cancer and Alzheimer's disease (AD) are considered) and the biosensor approach. A discussion of interesting current and future developments, not only in nucleic acid analysis, but also in gene therapy, concludes the article.
IntroductionOn Farm SamplingSampling at the AbattoirChoice of Detection Method
References
Verocytotoxin-producing Escherichia coli O157 is a serious pathogen in man that is carried by ruminants and has been isolated from some other animal species. Except
in the very young of certain species and in greyhounds, the organism is not associated with disease in animals. Humans may
be infected by ingestion of the organism through direct animal contact, from contaminated food or water or from the environment.
Great efforts have been made to improve hygienic food production and handling, to protect water supplies and to give adequate
advice to people handling animals. It is also essential to try to reduce the numbers of organisms shed by animals and, to
do this, a clear understanding of the ecology of the organism is required.
Shiga toxin-producing Escherichia coli (STEC) have been identified as a worldwide cause of serious human gastrointestinal disease and the life-threatening hemolytic uremic syndrome. The most common serotype implicated is E. coli O157:H7, but infections involving various non-O157 serotypes have been found with increasing frequency in many countries. Food-borne outbreaks caused by STEC can affect large numbers of people and cause serious morbidity, making the bacteria one of the most important emerging pathogens. Because there is no specific treatment of the disease currently available, there is an urgent need for effective preventive measures based on a detailed understanding of the epidemiology of STEC infections. Such measures will also be dependent on the availability of rapid, sensitive, and simple procedures for the detection of the pathogens both in human samples and in samples of nonhuman origin such as food. This review summarizes the current knowledge on the epidemiology of STEC infection and presents a survey of laboratory methods currently available for diagnosis of STEC. Special attention is given to new diagnostic procedures for the less readily detectable non-O157 STEC strains and to simple procedures, usually based on commercially available kits, that can be used in routine clinical microbiological laboratories.
Conventional culture-based methods for detection of E. coli O157:H7 in foods and water sources are time-consuming, and results can be ambiguous, requiring further confirmation by biochemical testing and PCR. A rapid immunoassay prior to cultivation to identify presumptive positive sample would save considerable time and resources. Immunomagnetic separation (IMS) techniques are routinely used for isolation of E. coli O157:H7 from enriched food and water samples, typically in conjunction with cultural detection followed by biochemical and serological confirmation. In this study, we developed a new method that combines IMS with fluorescence immunoassay, termed immunomagnetic fluorescence assay (IMFA), for the detection of E. coli O157:H7. E. coli O157:H7 cells were first captured by anti-O157 antibody-coated magnetic beads and then recognized by a fluorescent detector antibody, forming an immunosandwich complex. This complex was subsequently dissociated for measurement of fluorescence intensity with Signalyte™-II spectrofluorometer. Experiments were conducted to evaluate both linearity and sensitivity of the assay. Capture efficiencies were greater than 98%, as determined by cultural plating and quantitative real-time PCR, when cell concentrations were <10(5) cells/mL. Capture efficiency decreased at higher cell concentrations, due to the limitation of bead binding capacity. At lower cell concentrations (10-10(4) cells/mL), the fluorescence intensity of dissociated Cy5 solution was highly correlated with E. coli 157:H7 cell concentrations. The detection limit was 10 CFU per mL of water. The assay can be completed in less than 3 h since enrichment is not required, as compared to existing techniques that typically require a 24 h incubation for pre-enrichment, followed by confirmatory tests.
A 16-month old female child living on an Ontario dairy farm was taken to hospital suffering from bloody diarrhoea. Escherichia coli O157:H7 was isolated from her stool. Initial tests of well water samples were negative for E. coli by standard methods but culture of selected coliform colonies on sorbitol-MacConkey agar led to isolation of E. coli O157:H7. E. coli O157:H7 was also isolated from 63% of cattle on the farm. The E. coli O157:H7 isolates from the child, the water and the cattle were phage type 14, produced verotoxins 1 and 2, and were highly related on analysis by pulsed field gel electrophoresis. The child did not have known direct contact with the cattle and did not consume unpasteurized milk. Hydrogeological investigation revealed the design and location of the well would allow manure-contaminated surface water to flow into the well. This investigation demonstrates that cattle farm well water is a potential source of E. coli O157:H7 which may not be identified by standard screening for E. coli in water.
Bacteria inhibitory to Escherichia coli O157:H7 were isolated from cattle and evaluated for their potential for reducing carriage of E. coli O157:H7 in calves. Eighteen of 1,200 bacterial isolates from cattle feces and intestinal tissue samples were screened and determined to inhibit the growth of E. coli O157:H7 in vitro. Seventeen of the isolates were E. coli and one was Proteus mirabilis. None produced Shiga toxin. Genomic DNA fingerprinting by pulsed-field gel electrophoresis revealed 13 distinguishable profiles among the 18 isolates. Two calves inoculated perorally with a mixture of all 18 isolates (10(10) CFU) appeared to be normal and did not develop signs of clinical disease throughout a 25- to 27-day observation period. These bacteria colonized segments of the gastrointestinal tract and were in feces at the termination of the experiment (25 and 27 days postinoculation) at levels of 50 to 200 CFU/g. Fifteen cannulated calves were studied to determine the efficiency of the probiotic bacteria in reducing or eliminating the carriage of E. coli O157:H7. Nine calves served as controls, with each animal receiving perorally 10(10) CFU of E. coli O157:H7. E. coli O157:H7 was detected intermittently in the rumen samples from all control animals throughout 3 weeks postinoculation, whereas E. coli O157:H7 was shed at various levels in feces continuously throughout the experiment (mean, 28 days). E. coli O157:H7 was isolated from the rumens and colons of eight of nine and nine of nine calves, respectively, at the termination of the study. Six calves each received perorally 10(10) CFU of probiotic bacteria and then 2 days later received 10(10) CFU of E. coli O157:H7. E. coli O157:H7 was detected in the rumen for only 9 days postinoculation in two animals, for 16 days in one animal, for 17 days in two animals, and for 29 days in one animal. E. coli O157:H7 was detected in feces for only 11 days postinoculation in one animal, for 15 days in one animal, for 17 days in one animal, for 18 days in one animal, for 19 days in one animal, and for 29 days in one animal. At the end of the experiment (mean, 30 days), E. coli O157:H7 was not recovered from the rumen of any of the six animals treated with probiotic bacteria; however, E. coli O157:H7 was recovered from the feces of one of the animals. This animal was fasted twice postinoculation. These studies indicate that selected probiotic bacteria administered to cattle prior to exposure to E. coli O157:H7 can reduce the level of carriage of E. coli O157:H7 in most animals.
Microbial pathogens in food cause an estimated 6.5-33 million cases of human illness and up to 9,000 deaths in the United States each year. Over 40 different foodborne microbial pathogens, including fungi, viruses, parasites, and bacteria, are believed to cause human illnesses. For six bacterial pathogens, the costs of human illness are estimated to be $9.3-$12.9 billion annually. Of these costs, $2.9-$6.7 billion are attributed to foodborne bacteria. These estimates were developed to provide analytical support for USDA's Hazard Analysis and Critical Control Point (HACCP) systems rule for meat and poultry. (Note that the parasite Toxoplasma gondii is not included in this report.) To estimate medical costs and productivity losses, ERS uses four severity categories for acute illnesses: those who did not visit a physician, visited a physician, were hospitalized, or died prematurely. The lifetime consequences of chronic disease are included in the cost estimates for E. coli O157:H7 and fetal listeriosis.
Shiga-like toxin (verotoxin)-producing strains of Escherichia coli (SLTEC) originating from healthy cattle, sheep, goats, pigs, cats, and dogs were investigated for properties which are related to virulence of E. coli for humans. The slt-II (Shiga-like toxin II) and slt-IIc genes were frequent in SLTEC from healthy cattle and dogs but were rarely found in SLTEC from other animals. The slt-IIe gene was detected only in porcine SLTEC. SLTEC from goats and SLTEC from sheep were found to carry different SLT-II determinants which were not further characterized genetically. Sixty (28.8%) of 208 SLTEC from healthy animals showed diffuse adherence to HEp-2 cells. However, none of the strains was positive for genes specific for the local adherence (eaf), diffuse adherence (daa), or enteroaggregative (EAggEC) E. coli type. Only 3 (1.4%) of the 208 SLTEC were positive for attaching and effacing E. coli (eae) sequences. The enterohemolytic phenotype was present in 128 of the 208 SLTEC. Almost all enterohemolytic animal SLTEC were found to carry DNA sequences specific for the plasmid-encoded enterohemorrhagic E. coli hemolysin of E. coli O157. Bacteriophage-associated enterohemolysin (Ehly1 and Ehly2)-specific sequences were detected only in 14.4% of the 208 SLTEC and were linked with certain serotypes. The SLTEC from healthy animals constitute a very heterogeneous group of E. coli, and many of these strains appeared to be specific for their hosts. The absence of eae sequences in most animal SLTEC could indicate that these strains are less virulent for humans than the classical eae-positive enterohemorrhagic E. coli types.
Verotoxin-producing strains of Escherichia coli (VTEC), in particular serotype O157:H7, are now recognised as the major cause of haemorrhagic colitis and the haemolytic uraemic syndrome (HUS) in the U.K. and in North America, and increasingly so in other countries. Over a 3-year period (1989-1991), 16 cases of E. coli 0157 infection occurred in one town (Peterhead) in north-east Grampian. Four patients required admission to hospital, of whom three developed HUS. The bovine source of VTEC infection has now been clearly established with foodborne, waterborne, person-to-person and zoonotic transmission described. Despite extensive local enquiries, the source(s) of infection of the 16 cases in Peterhead was not established. Much still needs to be learned about the epidemiology, risk factors and long-term clinical sequelae of VTEC infection and HUS. Close collaboration between the medical and veterinary professions is of paramount importance in order to provide better understanding of the prevalence of E. coli O157 infection in cattle and the route(s) of transmission to humans.
A 3-year study of Escherichia coli infections in Grampian Region was conducted to ascertain the incidence, document clinical sequelae and identify at-risk groups. Approximately 30,000 stools from patients with acute diarrhoea were screened for E. coli O157, and an epidemiological questionnaire filled in for each patient whose stool was positive. Eighty-three patients were studied. The annual incidence was 6 per 100, 000. Proportionately more infections occurred in people involved in agriculture. Evidence was seen of case-to-case transmission, and contamination of a water supply. Eight cases developed haemolytic uraemic syndrome (HUS). There were 2 deaths due to HUS and 2 due to haemorrhagic colitis (HC). Symptomatic E. coli infection is relatively common in the Grampian Region, more common in the agricultural community, and is the main cause of HUS in this Region.
Outbreaks of foodborne viral gastroenteritis in England and Wales from 1992 to 1994 have been analysed using data from the national surveillance scheme for general outbreaks of infectious intestinal disease. The cause was virologically confirmed for 389 (31%) of the 1280 outbreaks for which a minimum set of data were collected. Forty-seven of the 389 were attributed to foodborne transmission, 41 of which were caused by small round structured viruses (SRSV). An infected food handler was suspected to be a contributing factor in 14 and the consumption of oysters in eight of these 41 foodborne SRSV outbreaks. No seasonal pattern emerged. The highest incidences occurred in Wales, West Midlands, and South Western regional health authorities. The annual rate of outbreaks did not increase during the three year period (Chi square for linear trend 0.6; p = 0.4). Much remains to be discovered about the epidemiology of foodborne viruses, and outbreaks present an opportunity to enhance our knowledge. As molecular diagnostic techniques become routinely available, it is likely that the role of viruses in foodborne outbreaks will be increasingly recognised.
There would appear to be little argument that the large outbreaks of E. coli O157:H7 which have occurred since the early 1980s represent a distinct, new phenomenon. The number of reported cases have increased dramatically, starting from zero in 1981; however, it is also clear that this increase in reported cases is in part an artifact of improved surveillance and reporting. Available data suggest that E. coli O157:H7 infections were present prior to 1982, although numbers appear to have been small. At a molecular level, the organism shows evidence of clonal origin, but there is not the striking clonality, with virtually identical pulsed-field gel electrophoresis and ribotyping patterns, which has been seen in situations such as the emergence of Vibrio cholerae O139 Bengal in the Indian subcontinent in 1992 or the introduction of V. cholerae O1 into naïve populations in South America in 1991 (127-129). Findings are more consistent with the image of an organism which arose from a common ancestor, but which has had time to become distributed geographically and to show some evidence of genetic divergence. While this is an "emerging" infection, at least in terms of its distribution and public recognition, it is unlikely that it will be possible to identify the "first" O157:H7 case or to track the clonal spread of the organism through cattle or human populations.
In 1992 the King's Fund organised the first London commission on the future of London's health services. The commission's recommendations, taken up in the Tomlinson report,1 led to radical and controversial changes in London's health services. In Spring 1997, a second London commission will issue its recommendations on the future of mental health services. London's Mental Health , published this week by the King's Fund, summarises the evidence on which the Commission will base its deliberations.2
London's Mental Health is a comprehensive overview of the capital's mental health services prepared by its foremost experts. This giant document may be reduced to four propositions: first, that London has uniquely high requirements for psychiatric services; second, that psychiatric services in inner London are “near collapse”; third, that the reason for this collapse is underfunding from central government, arising from a failure to take into account London's uniquely high requirements; and, fourth, that the …
There is no formal screening programme for glaucoma in Britain, and current practice can best be described as opportunistic surveillance, with no attempt to define clearly, or cover, the entire population at risk. To facilitate this surveillance, certain sections of the population are exempt from sight test charges, including first degree relatives of people with glaucoma, diabetic patients, and people receiving income support. However, probably about half of cases of glaucoma remain undiagnosed,1 and patients continue to present late in the course of the disease.
Detecting presymptomatic chronic glaucoma requires two independent events. Firstly, an individual must attend for a sight test, and, secondly, the practitioner must use appropriate tests: intraocular pressure measurement, optic disc assessment, and visual field testing–preferably all three.2 We know roughly how often optometrists perform tests for glaucoma from work done by the International Glaucoma Association,2 but until recently we lacked information on who consults optometrists and how often–particularly since charging for sight tests began in 1989. …
The antiphospholipid syndrome, first described in 1983,1 is now recognised as an important prothrombotic disorder associated with a specific group of antibodies. Its main clinical feature is thrombosis, both venous and arterial (especially recurrent cerebral ischaemic attacks). Other features include mild thrombocytopenia, chorea, heart valve disease, livedo reticularis, and, most commonly, recurrent pregnancy loss.2 The importance of the syndrome in general medicine, especially in vascular and neurological disease, is now acknowledged.
The syndrome has had various names. Hughes originally studied it in patients with systemic lupus erythematosus but recognised that most patients “had atypical lupus, or no lupus at all”–hence the concept of “primary” antiphospholipid syndrome.3 In the early 1990s it was found that a phospholipid binding protein, s2 glycoprotein I, …
The major causes of stroke in young adults and children differ from those in older people.1 Dissection of the internal carotid and vertebral arteries in the neck accounts for about a fifth of strokes in the young compared with about 2.5% in older patients.1
Dissection of intracranial blood vessels is rare and has a worse prognosis than extracranial dissections.2 Arterial dissection occurs when blood tracks into the vessel wall along a specific line of cleavage. This may be subintimal, causing luminal narrowing or occlusion, or subadventitial, when a pseudoaneurysm may form. The cause is rarely established and may differ according to the artery affected. The incidence of arterial dissection is increased in patients with fibromuscular dysplasia, migraine, or hypertension; in smokers; and in those taking oral contraceptives. It is commonly associated with trauma or manipulation to the neck.
Patients with dissection of the arteries in the neck may …
Britain's long awaited report on the ethics of xenotransplantation has now appeared.1 Following on from last year's report from the Nuffield bioethics committee,2 its main conclusion is that clinical trials of xenotransplantation are not appropriate at the present time as there is insufficient knowledge of the immune response to a xenograft, the physiological behaviour of a xenograft, and the risk of infection across species. Both reports conclude that it is ethical to use pigs as a source of donor tissues, provided that the pigs are well cared for, but not to use primates other than for carefully controlled research. However, in recommending that clinical trials should not yet be carried out the advisory group has taken a stronger line.
Is this recommendation reasonable …
Verotoxin producing Escherichia coli causes severe gastrointestinal disease, often with frank blood in the stool (haemorrhagic colitis). In about 2-7% of cases infection is complicated by haemolytic uraemic syndrome,1 which has a mortality of 3-5%. The current outbreak of infection with E coli 0157 in Scotland,2 described as “the second largest recorded outbreak anywhere,” is the subject of an interim report by Professor Hugh Pennington's expert group, produced with commendable speed.
Perhaps inevitably, the group has been able to discharge some parts of its remit better than others. With various legal proceedings pending, the first part of its remit—to examine the specific “circumstances which led to the outbreak”—receives only a brief reference. There are no descriptive or other data. Regarding the second part of its remit—“the implications for food safety and …
Cattle have been implicated as an important reservoir of Shiga-like toxin-producing Escherichia coli (SLTEC) O157:H7, enterohemorrhagic E. coli (EHEC) that cause hemorrhagic colitis and hemorrhagic uremic syndrome in humans. Naturally- or experimentally-infected cattle can shed low levels of E. coli O157:H7 long-term, but little is known about the pathogenesis of E. coli O157:H7 infection in cattle. E. coli O157:H7 induce characteristic attaching and effacing (A/E) mucosal lesions in ceca and colons of 1-day-old gnotobiotic piglets and this model is used to study the pathogenesis of SLTEC infections. A/E lesions were not detected in histologic sections of the intestines from adult cattle or 3- to 14-week-old calves infected with E. coli O157:H7. Our objective was to determine if E. coli O157:H7 induce A/E lesions in neonatal calves. Colostrum-deprived calves (< 12-h-old) were bottle-fed with antibiotic-free milk replacer containing 10(10) colony forming units (CFU) of O157:H7 (SLT-I+, SLT-II+) or nonpathogenic E. coli, necropsied 18 h postinfection and their intestines examined histologically. Bacterial attachment, effacement of microvillous borders, and destruction of epithelium were observed in the intestines of the neonatal calves inoculated with E. coli O157:H7. No lesions were observed in calves inoculated with nonpathogenic E. coli. The distribution of intestinal lesions in neonatal calves resembled that in gnotobiotic pigs. Neonatal calves are apparently more susceptible to A/E lesions induced by E. coli O157:H7 than are older calves or adult cattle and provide a model for studying the pathogenesis of E. coli O157:H7 infections in cattle.
Cattle arriving for slaughter at abattoirs in the Veneto region of N. Italy were examined for intestinal carriage of Escherichia coli O157. Rectal swabs were cultured in modified buffered peptone water and E. coli O157 was concentrated by an immunomagnetic separation technique; the magnetic beads were cultured onto cefixime tellurite sorbitol MacConkey agar. Sorbitol non-fermenting E. coli O157 was isolated from 15 (3.6%) of 419 feedlot cattle but not from 437 veal calves or 65 culled cows. All strains of E. coli O157 hybridized with DNA probes specific for the VT1 or VT2 genes, but two strains did not produce toxin detectable by Vero cell assay. Six different plasmid profiles were observed with all strains harbouring the large 93 kb plasmid characteristic of VTEC. Six strains produced urease but otherwise strains were biochemically typical of E. coli O157. One strain was resistant to streptomycin, tetracycline and sulphonamides but the remainder were sensitive to all antimicrobials tested. This is the first description of the isolation of verocytotoxin-producing E. coli O157 from cattle in Italy. As the contamination of bovine carcasses with E. coli O157 during slaughter and processing has been demonstrated, the risk of transmission of this organism from beef cattle to the human population in the Veneto region, through foods of bovine origin or by other routes, should not be overlooked.
Fecal samples from slaughtered cattle were studied for enterohaemorrhagic Escherichia coli (EHEC) by DNA hybridization with biotin-labelled DNA probes specific for the EHEC virulence plasmid, Shiga-like toxin I (SLT I), Shiga-like toxin II (SLT II) and eae gene. Among 136 animals analysed, 47 (34.5%) were found to carry EHEC. The cytotoxic genotypes observed for EHEC strains were: 60.4% SLT I, 12.5% SLT II and 10.4% SLT I + SLT II; 16.7% resulted SLT I and SLT II negative. A total of 14 out of 48EHEC strains (29.2%) hybridized with a fimbrial probe and 14 of 48 strains with an sas probe. An important number of strains (18 out of 48) belonged to serogroups O157, O26 and O111, serogroups also commonly isolated from haemolytic uremic syndrome cases in Chile. While EHEC isolates from the same animal were usually of the same serogroup, one animal was found to carry two EHEC strains of different serogroups. A total of 50% of EHEC strains were sorbitol negative, irrespective of the O serogroup or EHEC genotypic profile. Results obtained in this study strongly suggest that cattle in Chile are a reservoir of EHEC associated with disease in humans.
The persistence of Escherichia coli O157:H7 in cattle and the farm environment was investigated on eight Ontario dairy farms positive for E. coli O157:H7 in a longitudinal study commenced one year previously. Faecal samples from cows, calves, humans, cats, rodents, wild birds, a composite fly sample and numerous composite and individual environmental samples were cultured and tested for verotoxin-producing E. coli (VTEC). VTEC isolates were serotyped and E. coli O157:H7 isolates were phage typed. E. coli O157:H7 phage type 34 was isolated from one calf on each of two farms. The same phage type had been isolated on one of these farms 12 months earlier. Most E. coli O157:H7-positive animals and farms became culture-negative within 2 and 3 months, respectively. E. coli O157:H7 was not isolated from any environmental samples, although evidence of VTEC was found in composite samples from calf feeders (19.1%), calf barn surfaces (18%), cow feeders (14.9%), flies (12.5%), cow barn surfaces (11.3%), and individual milk filters (12.5%). VTEC belonging to 21 non-O157 serotypes were isolated from 24 cows (8.2%), 21 calves (18.3%), 2 cow feeder samples (3.0%), and 1 calf feeder sample (4.8%). Shedding of E. coli O157:H7 by infected dairy cattle appears to be transient and persistence of E. coli O157:H7 was not demonstrated from the farm environment sites tested.
We examined 1,266 fecal specimens from healthy cattle during the investigations of two sporadic cases of hemolytic uremic syndrome associated with raw milk consumption and an outbreak of gastroenteritis and hemolytic uremic syndrome caused by Escherichia coli serotype O157:H7. We collected specimens from heifers, calves, and adult cows on 22 farms, in a stockyard, and in a packing house. We also collected 3 raw hamburger specimens from a restaurant and 23 raw milk samples from two farms. All specimens were examined for E. coli O157:H7 by using sorbitol-MacConkey agar, H immobilization, O157 agglutination, and tissue culture cytotoxicity. E. coli O157:H7 was isolated from 16 heifers or calves and 1 adult cow on 22 farms, 1 stockyard calf, 2 beef specimens, and 1 raw milk sample. Selected fecal specimens were also examined for the presence of other Shiga-like-toxin-producing E. coli (SLTEC) by testing polymyxin B extracts of colony sweeps and then testing individual colonies for toxin production. SLTEC other than O157 was isolated from 8 of 10 farms investigated and from the stockyard; 8% of adult cows and 19% of heifers and calves were positive for SLTEC. Several animals were positive for SLTEC by colony sweep only. This investigation demonstrates that dairy cattle are a reservoir of E. coli O157:H7 and other SLTEC.
In Canada, the number of human isolates of verotoxigenic (VT + ve) Escherichia coli O157:H7 from diarrhoeal cases and haemolytic uraemic syndrome and haemorrhagic colitis has increased from 25 in 1982 to 2384 in 1989. A total of 3273 VT + ve E. coli O157:H7 strains (3255 strains isolated in Canada and 18 isolates from other countries) were phage typed. The phage typing scheme has been extended from 14 to 62 phage types. Of these, five types occurred exclusively in other countries (type 47 in Japan; and types 49, 50, 51 and 52 in the U.K.). Thirty-five different phage types were identified in Canada; only nine of these (1, 2, 4, 8, 14, 21, 23, 31 and 32), each accounted for more than 1% of the cases from human sources. The same nine types were the only ones observed among the isolates from non-human sources (meat and slaughter houses) suggesting a food-borne transmission in most of the human cases. Phage types 1 (30.5%); 4 (21%); 8 (13.5%); 31 (8.9%) and 14 (8%) were encountered in varying frequencies in most of the provinces; infrequently occurring phage types also showed regional variation. Thirteen different phage types were identified among 151 outbreaks representing 556 isolates of E. coli O157:H7. More than one phage type were encountered in 12 outbreaks whereas in 141 outbreaks, all strains in each, had the same phage type.
To determine the effect of low dose interferon alfa (human lymphoblastoid interferon) on aminotransferase activities in chronic non-A non-B hepatitis.
Prospective randomised controlled parallel group study of active treatment versus no treatment carried out over 16 weeks and preceded by baseline measurements at weeks 8 and 4 and time zero.
HEPATOLOGY outpatient clinics in secondary referral centres.
Fourteen adults with histologically proved chronic hepatitis and persistently raised aminotransferase activities for six months or more.
Seven patients randomised to receive interferon alfa 5 megaunits (MU) daily for one week, reducing to 5 MU thrice weekly for seven weeks, then 3 MU thrice weekly for eight weeks. Controls not treated.
Control of hepatic enzyme activity in chronic non-A non-B hepatitis.
Serum aspartate aminotransferase activity remained raised in controls (mean increase in study period 23.4 U/l) but fell rapidly to normal in the treated group (mean decrease 106.4 U/l). In four cases values were normal by eight weeks and in five cases by 16 weeks. Only minor side effects were recorded (fever, myalgia), which became less common as treatment progressed.
Continuous low dose interferon alfa reduces aspartate aminotransferase activity to normal in most patients with chronic non-A non-B hepatitis and may prevent progression to cirrhosis.
The chronic Epstein-Barr virus syndrome is a poorly defined symptom complex characterized primarily by chronic or recurrent debilitating fatigue and various combinations of other symptoms, including sore throat, lymph node pain and tenderness, headache, myalgia, and arthralgias. Although the syndrome has received recent attention, and has been diagnosed in many patients, the chronic Epstein-Barr virus syndrome has not been defined consistently. Despite the name of the syndrome, both the diagnostic value of Epstein-Barr virus serologic tests and the proposed causal relationship between Epstein-Barr virus infection and patients who have been diagnosed with the chronic Epstein-Barr virus syndrome remain doubtful. We propose a new name for the chronic Epstein-Barr virus syndrome—the chronic fatigue syndrome—that more accurately describes this symptom complex as a syndrome of unknown cause characterized primarily by chronic fatigue. We also present a working definition for the chronic fatigue syndrome designed to improve the comparability and reproducibility of clinical research and epidemiologic studies, and to provide a rational basis for evaluating patients who have chronic fatigue of undetermined cause.
Verocytotoxin (VT)-producing Escherichia coli (VTEC) are a newly recognized group of enteric pathogens which are increasingly being recognized as common causes of diarrhea in some geographic settings. Outbreak studies indicate that most patients with VTEC infection develop mild uncomplicated diarrhea. However, a significant risk of two serious and potentially life-threatening complications, hemorrhagic colitis and the hemolytic uremic syndrome, makes VTEC infection a public health problem of serious concern. The main reservoirs of VTEC appear to be the intestinal tracts of animals, and foods of animal (especially bovine) origin are probably the principal sources for human infection. The term VT refers to a family of subunit exotoxins with high biological activity. Individual VTEC strains elaborate one or both of at least two serologically distinct, bacteriophage-mediated VTs (VT1 and VT2) which are closely related to Shiga toxin and are thus also referred to as Shiga-like toxins. The holotoxins bind to cells, via their B subunits, to a specific receptor which is probably the glycolipid, globotriosyl ceramide (Gb3). Binding is followed by internalization of the A subunit, which, after it is proteolytically nicked and reduced to the A1 fragment, inhibits protein synthesis in mammalian cells by inactivating 60S ribosomal subunits through selective structural modification of 28S ribosomal ribonucleic acid. The mechanism of VTEC diarrhea is still controversial, and the relative roles of locally acting VT and "attaching and effacing adherence" of VTEC to the mucosa have yet to be resolved. There is increasing evidence that hemolytic uremic syndrome and possibly hemorrhagic colitis result from the systemic action of VT on vascular endothelial cells. The role of antitoxic immunity in preventing the systemic complications of VTEC infection is being explored. Antibiotics appear to be contraindicated in the treatment of VTEC infection. The most common VTEC serotype associated with human disease is O157:H7, but over 50 different VT-positive O:H serotypes have now been identified. The best strategies for diagnosing human VTEC infection include testing for the presence of free VT in fecal filtrates and examining fecal cultures for VTEC by means of deoxyribonucleic acid probes that specify genes encoding VT1 and VT2. Both methods are currently confined to specialized laboratories and await commercial development for wider use. In the meantime, most laboratories should continue to screen for the most common human VTEC serotype, O157:H7, using a sorbitol-containing MacConkey medium.
In a group of patients who suffered from chronic ill health after an attack of acute infectious mononucleosis a disorder of T cell regulation was found. By means of cytochemical reactions the staining pattern associated with T suppressor cells was found in a greater percentage and that associated with T helper cells in a smaller percentage than in normal subjects. In a few patients this finding was confirmed in a functional suppressor assay. The patients were unwell for at least a year but most later made a complete recovery, which was associated with return to normal of the lymphocyte subsets.
Yap Let al. Randomised controlled trial oflympho-bIastoid interferon-a in European men with chronic hepatitis B infec-tion
- Brook Mg Chan
Brook MG. Chan G. Yap Let al. Randomised controlled trial oflympho-bIastoid interferon-a in European men with chronic hepatitis B infec-tion. BMJ 1989;299:652-6.
which made the strain more virulent for mice than original lyophilized cultures [7]. BALB/c mice (29-to 35-day-old females, 15-16 g; Charles River Canada, St. Constant) were used. Ciprofl.oxacin (Miles Canada, Etobicoke) was encapsulated within multilamellar li-posomes
- Kirby
at 37°C with 5% CO 2, which made the strain more virulent for mice than original lyophilized cultures [7]. BALB/c mice (29-to 35-day-old females, 15-16 g; Charles River Canada, St. Constant) were used. Ciprofl.oxacin (Miles Canada, Etobicoke) was encapsulated within multilamellar li-posomes prepared by a modified method of Kirby and Gregoria-dis