Verocytotoxin-producing Escherichia Coli O157 Research Articles

School outbreak of Escherichia coli O157 with high levels of transmission, Staffordshire, England, February 2012.

Verocytotoxin-producing Escherichia coli (VTEC) are bacteria that cause infectious gastroenteritis and in certain settings can cause widespread infection due to secondary transmission. We describe the findings of an investigation of a school-based outbreak of VTEC in Staffordshire, England. Outbreak investigation at a school in February 2012 after two children were diagnosed with VTEC infection. Cases were defined as pupils and staff (or their household contacts) with gastrointestinal symptoms or asymptomatic screened persons, with laboratory confirmed VTEC O157 infection (phage type 32, verocytotoxin 2) occurring on or after 1 February 2012. Microbiological tests of food and faecal samples plus screening of asymptomatic contacts were undertaken. Epidemiological and clinical data were descriptively analysed. Thirty-eight cases were detected. Nineteen were asymptomatic and identified via screening of 191 pupils. Infection was introduced into the school from an earlier household cluster, followed by extensive person-to-person transmission within the nursery/infant group with limited spread to the wider school population. Control measures included several interventions, in particular, universal screening of pupils and staff. Screening during school outbreaks is not underpinned by guidance but proved to be a key control measure. Screening of asymptomatic contacts should be considered in similar outbreaks.

Identification of two allelic variants of toxB gene and investigation of their distribution among Verocytotoxin-producing Escherichia coli

Verocytotoxin-producing Escherichia coli (VTEC) are food borne pathogens causing severe human infections. The virulence genes asset of VTEC is complex and has not been completely defined yet. Nonetheless, all the virulence genes described so far have been described as conveyed by mobile genetic elements. A gene, termed toxB, has been identified in a large virulence plasmid of VTEC O157, later described in similar plasmids carried by VTEC O26 and O145. In this study we identified for the first time an intact copy of toxB gene in a plasmid present in a VTEC O111 strain and observed the existence of two allelic variants of the gene, that we termed toxB1 and toxB2. We investigated the distribution of the two alleles in a panel of VTEC strains belonging to different serogroups and demonstrated that this gene is present only in VTEC serogroups associated with the most severe forms of the infections such as those belonging to the five serogroups O157, O26, O111, O103 and O145 and that the two alleles segregate with the serogroup of the hosting strains. In particular the toxB1 variant was only present in VTEC O157 while the toxB2 allele was present in the remaining four VTEC serogroups.

Identification and characterization of a peculiar vtx2-converting phage frequently present in verocytotoxin-producing Escherichia coli O157 isolated from human infections.

Certain verocytotoxin-producing Escherichia coli (VTEC) O157 phage types (PTs), such as PT8 and PT2, are associated with severe human infections, while others, such as PT21, seem to be restricted to cattle. In an attempt to delve into the mechanisms underlying such a differential distribution of PTs, we performed microarray comparison of human PT8 and animal PT21 VTEC O157 isolates. The main differences observed were in the vtx2-converting phages, with the PT21 strains bearing a phage identical to that present in the reference strain EDL933, BP933W, and all the PT8 isolates displaying lack of hybridization in some regions of the phage genome. We focused on the region spanning the gam and cII genes and developed a PCR tool to investigate the presence of PT8-like phages in a panel of VTEC O157 strains belonging to different PTs and determined that a vtx2 phage reacting with the primers deployed, which we named Φ8, was more frequent in VTEC O157 strains from human disease than in bovine strains. No differences were observed in the production of the VT2 mRNA when Φ8-positive strains were compared with VTEC O157 possessing BP933W. Nevertheless, we show that the gam-cII region of phage Φ8 might carry genetic determinants downregulating the transcription of the genes encoding the components of the type III secretion system borne on the locus of enterocyte effacement pathogenicity island.

Incidence and Virulence Determinants of Verocytotoxin-Producing Escherichia coli Infections in the Brussels-Capital Region, Belgium, in 2008–2010

The incidence of verocytotoxin-producing Escherichia coli (VTEC) was investigated by PCR in all human stools from Universitair Ziekenhuis Brussel (UZB) and in selected stools from six other hospital laboratories in the Brussels-Capital Region, Belgium, collected between April 2008 and October 2010. The stools selected to be included in this study were those from patients with hemolytic-uremic syndrome (HUS), patients with a history of bloody diarrhea, patients linked to clusters of diarrhea, children up to the age of 6 years, and stools containing macroscopic blood. Verocytotoxin genes (vtx) were detected significantly more frequently in stools from patients with the selected conditions (2.04%) than in unselected stools from UZB (1.20%) (P = 0.001). VTEC was detected most frequently in patients with HUS (35.3%), a history of bloody diarrhea (5.15%), or stools containing macroscopic blood (1.85%). Stools from patients up to the age of 17 years were significantly more frequently vtx positive than those from adult patients between the ages of 18 and 65 years (P = 0.022). Although stools from patients older than 65 years were also more frequently positive for vtx than those from patients between 18 and 65 years, this trend was not significant. VTEC was isolated from 140 (67.9%) vtx-positive stools. One sample yielded two different serotypes; thus, 141 isolates could be characterized. Sixty different O:H serotypes harboring 85 different virulence profiles were identified. Serotypes O157:H7/H- (n = 34), O26:H11/H- (n = 21), O63:H6 (n = 8), O111:H8/H- (n = 7), and O146:H21/H- (n = 6) accounted for 53.9% of isolates. All O157 isolates carried vtx2, eae, and a complete O island 122 (COI-122); 15 also carried vtx1. Non-O157 isolates (n = 107), however, accounted for the bulk (75.9%) of isolates. Fifty-nine (55.1%) isolates were positive for vtx1, 36 (33.6%) were positive for vtx2, and 12 (11.2%) carried both vtx1 and vtx2. Pulsed-field gel electrophoresis revealed wide genetic diversity; however, small clusters of O157, O26, and O63:H6 VTEC that could have been part of unidentified outbreaks were identified. Antimicrobial resistance was observed in 63 (44.7%) isolates, and 34 (24.1%) showed multidrug resistance. Our data show that VTEC infections were not limited to patients with HUS or bloody diarrhea. Clinical laboratories should, therefore, screen all stools for O157 and non-O157 VTEC using selective media and a method for detecting verocytotoxins or vtx genes.

Development of a multiplex PCR for rapid detection of verocytotoxin-producing Escherichia coli O26 in raw milk and ground beef.

Verocytotoxin-producing Escherichia coli (VTEC) O26 is an emergent pathotype that has caused an increasing number of sporadic cases and outbreaks of gastroenteritis, hemorrhagic colitis, and hemolytic uremic syndrome in the United States and Europe. Many cases are associated with the consumption of milk and undercooked or fermented meats. The stx(2) strains of VTEC O26 seem to be more likely to cause human infections than isolates expressing only stx(1). The isolation and identification of VTEC O26 from foods is labor intensive and time-consuming. We developed a multiplex PCR (M-PCR) assay for the identification and characterization of E. coli O26 VTEC and its detection in raw milk and ground beef. The method is based on the amplification of the wzx, stx(1), and stx(2) genes for the simultaneous detection of the O26 antigen and verocytotoxin types 1 and 2. This M-PCR assay had a sensitivity of 10(8) CFU/ml when applied to a bacterial suspension and of 10(6) CFU/ml or g when applied to both inoculated milk and minced beef samples. This M-PCR assay also was highly specific, and results were consistently negative for negative controls (nonpathogenic E. coli strains, uninoculated milk and beef samples, and samples inoculated with the nontarget microorganisms). This method could be used for the rapid detection of E. coli O26 VTEC from foods and for the rapid identification and characterization of clinical and environmental isolates.

Virulence Profiling and Quantification of Verocytotoxin-ProducingEscherichia coliO145:H28 and O26:H11 Isolated During an Ice Cream–Related Hemolytic Uremic Syndrome Outbreak

In September-October 2007, a mixed-serotype outbreak of verocytotoxin-producing Escherichia coli (VTEC) O145:H28 and O26:H11 occurred in the province of Antwerp, Belgium. Five girls aged between 2 and 11 years developed hemolytic uremic syndrome, and seven other coexposed persons with bloody diarrhea were identified. Laboratory confirmation of O145:H28 infection was obtained for three hemolytic uremic syndrome patients, one of whom was coinfected with O26:H11. The epidemiological and laboratory investigations revealed ice cream as the most likely source of the outbreak. The ice cream was produced at a local dairy farm using pasteurized milk. VTEC of both serotypes with indistinguishable pulsed-field gel electrophoresis patterns were isolated from patients, ice cream, and environmental samples. Quantitative analysis of the ice cream indicated concentrations of 2.4 and 0.03 CFU/g for VTEC O145 and O26, respectively. Virulence typing revealed that the repertoire of virulence genes carried by the O145:H28 outbreak strain was comparable to that of O157 VTEC and more exhaustive as compared to the O26:H11 outbreak strain and nonrelated clinical strains belonging to these serotypes. Taken together, these data suggest that O145:H28 played the most important role in this outbreak.

Prevalence of Escherichia coli O157 and verocytotoxin producing E. coli (VTEC) on Danish beef carcasses

The prevalence of verocytotoxin producing Escherichia coli (VTEC), E. coli O157, and VTEC O157 in 474 swab samples from Danish beef carcasses was determined. The presence of E. coli O157 was determined by a culture method that included immunomagnetic separation (IMS) followed by real time PCR testing of isolates for verocytotoxin ( vtx) genes. E. coli O157 was recovered from 4.2% of the carcass samples and VTEC O157 from 3.4% of the samples. All VTEC O157 contaminated carcasses were from bull calves and the VTEC O157 prevalence on bull calf carcasses was 7.3%. The VTEC O157 contaminated beef carcasses were sampled again after one week of cold storage, and 15 of the 16 carcasses were then VTEC O157 negative. The presence of VTEC was determined by a duplex real time PCR assay for vtx1 and vtx2 in DNA from enrichment cultures of swabs. In total 45.4% of the samples were VTEC positive. VTEC were isolated from 21% of 77 vtx-positive samples that were identified by replication of colonies on hydrophobic grid membrane filters followed by hybridisation with vtx specific DNA probes. Fourteen of the 16 VTEC isolates were non-O157 and these strains were negative for the virulence gene eae. A real time PCR assay for the E. coli O157 specific rfbE gene was developed. In total 22.4% of the enriched samples were positive for the O157 rfbE gene. The combined results of the vtx and rfbE real time PCR screening showed that 17.5% of the carcasses potentially were contaminated with VTEC O157. Screening of carcass swabs was expanded by real time PCR testing for eae in a subset of the samples. Of 244 samples, 25.4% were positive for both vtx and eae. The eae gene was detected in 81% of the vtx-positive samples and in 46% of 67 vtx-negative samples, indicating that bacteria harbouring eae are widespread on bovine carcasses. The present study shows that real time PCR screening of carcass samples for genes encoding virulence or other genetic markers is a reliable method for rapid identification of carcasses that potentially are contaminated with VTEC.

Experimental infection in calves with a specific subtype of verocytotoxin-producing Escherichia coli O157:H7 of bovine origin

BackgroundIn Sweden, a particular subtype of verocytotoxin-producing Escherichia coli (VTEC) O157:H7, originally defined as being of phage type 4, and carrying two vtx2 genes, has been found to cause the majority of reported human infections during the past 15 years, including both sporadic cases and outbreaks. One plausible explanation for this could be that this particular subtype is better adapted to colonise cattle, and thereby may be excreted in greater concentrations and for longer periods than other VTEC O157:H7 subtypes.MethodsIn an experimental study, 4 calves were inoculated with 109 colony forming units (cfu) of strain CCUG 53931, representative of the subtype VTEC O157:H7 (PT4;vtx2;vtx2c). Two un-inoculated calves were co-housed with the inoculated calves. Initially, the VTEC O157:H7 strain had been isolated from a dairy herd with naturally occurring infection and the farm had previously also been linked to human infection with the same strain. Faecal samples were collected over up to a 2-month period and analysed for VTEC O157 by immuno-magnetic separation (IMS), and IMS positive samples were further analysed by direct plating to elucidate the shedding pattern. Samples were also collected from the pharynx.ResultsAll inoculated calves proved culture-positive in faeces within 24 hours after inoculation and the un-inoculated calves similarly on days 1 and 3 post-inoculation. One calf was persistently culture-positive for 43 days; in the remainder, the VTEC O157:H7 count in faeces decreased over the first 2 weeks. All pharyngeal samples were culture-negative for VTEC O157:H7.ConclusionThis study contributes with information concerning the dynamics of a specific subtype of VTEC O157:H7 colonisation in dairy calves. This subtype, VTEC O157:H7 (PT4;vtx2;vtx2c), is frequently isolated from Swedish cattle and has also been found to cause the majority of reported human infections in Sweden during the past 15 years. In most calves, inoculated with a representative strain of this specific subtype, the numbers of shed bacteria declined over the first two weeks. One calf could possibly be classified as a high-shedder, excreting high levels of the bacterium for a prolonged period.

Human infections with verocytotoxin-producing Escherichia coli O157 – 10 years of E. coli O157 serodiagnosis

From 1997 to 2007, the Laboratory of Enteric Pathogens (LEP), Health Protection Agency, UK, received sera from 2148 patients for testing for antibodies to the LPS of verocytotoxin-producing Escherichia coli (VTEC) O157. A total of 676 (31.5 %) sera had antibodies binding the LPS of E. coli O157 and the majority of patients were below the age of 10 years, a trend observed for both males and females. Antibody-positive patients had haemolytic uraemic syndrome (HUS) in 79.3 % of cases and most of these presented with the atypical (D-) form of HUS. Nine patients were shown to have antibodies to the LPS of E. coli belonging to serogroups O26 (4), O103 (2), O111 (1) and O145 (2) and one patient had antibodies to the somatic antigens of both E. coli O26 and O103. The serodiagnosis of infections with E. coli O157 and other VTEC continues to be an important adjunct to bacteriology. Where clinicians suspect the involvement of a VTEC in disease, patients' sera should be submitted to the LEP for analysis without delay.

Cefixime-tellurite rhamnose MacConkey agar for isolation of Vero cytotoxin-producingEscherichia coliserogroup O26 from Scottish cattle and sheep faeces

To compare rhamnose MacConkey agar supplemented with cefixime and tellurite (CT-RMac) and tryptone bile X-glucuronide (TBX) agars as isolation media for Vero cytotoxin-producing Escherichia coli (VTEC) serogroup O26 from animal faeces. Nine VTEC O26 were isolated from sheep faeces; out of which six were isolated only on CT-RMac and one was isolated only on TBX. One hundred and twelve VTEC O26 were isolated from calf faeces; out of which 97% were from CT-RMac and 52% were from TBX. In a study of E. coli O26 strains, 84% of VT-positive O26 did not ferment rhamnose when compared with 16% of VT-negative O26. VT-positive (19%) and VT-negative (39%) E. coli O26 strains did not grow on CT-RMac agar. It is important to consider that VTEC O26 strains either may ferment rhamnose or may be sensitive to the CT supplement of CT-RMac agar. This work compares CT-RMac and TBX agars as isolation medium for VTEC O26 from Scottish animal faeces and highlights that VTEC O26 may be missed if only CT-RMac agar is used.

Outbreak of verocytotoxin-producing E. coli O145 and O26 infections associated with the consumption of ice cream produced at a farm, Belgium, 2007

In October 2007, an outbreak of verocytotoxin-producing Escherichia coli (VTEC) O145 and E. coli O26 occurred among consumers of ice cream produced and sold in September 2007 at a farm in the province of Antwerp (Belgium). The ice cream was consumed at two birthday parties and also eaten at the farm. Five children, aged between two and 11 years, developed haemolytic uraemic syndrome (HUS), and seven other co-exposed persons contracted severe diarrhoea. In three of the five HUS cases VTEC O145 infections were laboratory confirmed, one in association with VTEC O26. Identical isolates of E. coli O145 and O26 were detected with PCR and PFGE in faecal samples of patients and in ice cream leftovers from one of the birthday parties, in faecal samples taken from calves, and in samples of soiled straw from the farm at which the ice cream was produced. Ice cream was made from pasteurised milk and most likely contaminated by one of food handlers.

An investigation of factors associated with the prevalence of verocytotoxin producing Escherichia coli O157 shedding in Scottish beef cattle

The prevalence of verocytotoxin-producing Escherichia coli (VTEC) O157 in 12–30-month-old beef finishing cattle in Scotland was determined using 1g faeces samples enriched in buffered peptone water, followed by immunomagnetic separation (IMS) and isolation on sorbitol MacConkey agar with cefixime and tellurite supplement (CT-SMAC). A validated questionnaire was used to collect information that could be associated with the samples. Generalised Linear Models and Generalised Linear Mixed Models were used to identify factors associated with shedding both between and within groups.A total of 14,856 samples were collected from 952 farms, of which 1231 were positive for VTEC O157. Prevalence levels were calculated with 95% confidence intervals as follows: 7.9% (6.5%, 9.6%) of animals sampled were estimated to be shedding VTEC O157, while 22.8% (19.6%, 26.3%) of farms were estimated as having at least one animal shedding in the group sampled. The median percentage of animals shedding in positive groups was 25% (20%, 32%).An increased probability of a group containing a shedding animal was associated with larger numbers of finishing cattle, the presence of pigs on the farm, or the farm being classed as a dairy unit stocking beef animals. Farms that spread slurry on grazing land were more likely to have shedding animals, while those that spread manure were at lower risk. Groups with older animals were less likely to be identified as positive. There was no significant regional difference in group shedding probabilities, but the proportion of positive groups dropped over two successive years of the study. Higher mean levels of shedding in positive groups were associated with animals being housed rather than at pasture, and this effect was stronger in groups which had recently had a change in housing or diet. Farms with animals at pasture had lower mean prevalence where water was supplied from a natural source, as had farms with higher numbers of finishing cattle. There remained unexplained variability in mean prevalence levels on positive farms in different areas of Scotland.

Detection of Verocytotoxin-Producing Escherichia coli Serogroups O157 and O26 in the Cecal Content and Lymphatic Tissue of Cattle at Slaughter in Italy

Verocytotoxin-producing Escherichia coli (VTEC) has emerged as a foodborne pathogen that can cause severe and potentially fatal illnesses, such as hemorrhagic colitis or the hemolytic uremic syndrome. In this study, 182 cattle at slaughter (119 dairy cows and 63 feedlot cattle) were randomly selected and tested for the presence of VTEC serogroups O26, O103, O111, O145, and O157 in their cecal content and lymphatic tissue (tonsils or mesenteric lymph nodes). A total of 364 samples were evaluated with an immunomagnetic separation technique followed by slide agglutination. Presumptive VTEC O26, O103, O111, O145, and O157 isolates were tested by Vero cell assay for verocytotoxin production and by multiplex PCR assay for the detection of vtx1, vtx2, eae, and E-hlyA genes. VTEC O157 was detected in 6 (3.3%) of 182 animals, and VTEC O26 was detected in 1 (0.5%) of 182 animals. No VTEC O103, VTEC O111, or VTEC O145 isolates were found in cattle feces, but one VTEC O91:H−vtx2+, eae−, E-hlyA+ strain nonspecifically cross-reacted with the VTEC O103 type. The prevalence of VTEC O157 in the lymphatic tissue of cattle was 1.1% in both tonsils (1 of 93 samples) and mesenteric lymph nodes (1 of 89 samples). Lymphatic tissue contamination was observed only in VTEC O157 intestinal carriers; two (33.3%) of six fecal carriers were simultaneously VTEC O157 lymphatic carriers. This finding suggests that VTEC O157 contamination of meat does not necessarily come from feces or the environment. No other VTEC serogroups were detected in the lymphatic tissue of slaughtered cattle.

Intraserotype diversity among Argentinian verocytotoxigenic Escherichia coli detected by random amplified polymorphic DNA analysis

Most cases of diarrhoea-associated haemolytic uraemic syndrome (HUS) are caused by verocytotoxin-producing Escherichia coli (VTEC). Argentina has the highest worldwide incidence of HUS, but with a lower incidence of VTEC O157 : H7 serotype than non-Latin American countries. A large number of VTEC serotypes have been isolated from cattle and cattle-derived food products in Argentina. The aim of this work was to study intraserotype genetic diversity among these VTEC strains by random amplification of polymorphic DNA (RAPD). Strains were selected that belonged to the same serotype, but had been isolated from different sources (cattle and meat). Intraserotype genetic diversity was detected among strains belonging to O20 : H19, O113 : H21, O117 : H7, O157 : H7, O171 : H2 and O174 : H21, but only one RAPD profile corresponded to strains belonging to O91 : H21, although these isolates were from different sources.

First general outbreak of Verocytotoxin-producing Escherichia coli O157 in Denmark.

This report describes the first general outbreak of verocytotoxin-producing E. coli (VTEC) in Denmark. Twenty five patients, 18 children and seven adults, with culture-confirmed VTEC O157:H- infection and indistinguishable pulsed-field gel electrophoresis DNA profiles, were identified during a six month period from September 2003 to March 2004. The outbreak strain possessed the virulence genes: eae, vtx1 and vtx2c. All patients but one presented with diarrhoea; none developed haemolytic uraemic syndrome. The outbreak was restricted to Copenhagen and surrounding areas. A case-control study including 11 cases and 55 matched controls revealed an association between VTEC O157:H- infection and shopping in a specific supermarket chain in Copenhagen and surrounding area, matched odds ratio (OR): 8.7 (95% confidence interval (CI): 1.1-71). After exclusion of three assumed secondary cases, only consumption of a particular kind of organic milk from a small dairy was associated with disease OR: 8.7 (95% CI 1.6-48). Environmental and microbiological investigations at the suspected dairy did not confirm the presence of the outbreak strain, but the outbreak stopped once the dairy was closed and thoroughly cleaned.

A longitudinal study of Escherichia coli O157 in cattle of a Dutch dairy farm and in the farm environment

From July 1999 till November 2000, a longitudinal study was conducted on a dairy farm in The Netherlands to study within herd prevalence and types of verocytotoxin producing Escherichia coli (VTEC) of serogroup O157 over time, and determine environmental reservoirs and possible transmission routes. Faeces, blood, milk and environmental samples were collected 14 times with intervals varying from 4 to 10 weeks during the study period. Faecal samples were selectively cultured for Escherichia coli O157. Isolates were tested by PCR for the most common virulence genes, VTI, VTII and eae, and typed by pulsed field gel electrophoresis. In total, 71 isolates were obtained, of which 49 from dairy cows, 8 from young stock, 5 from other animals and 9 from the environment. Positive samples were all detected in summer and early fall. VT- and eae-genes were found in all tested isolates, except in one. DNA typing showed that three clusters of O157 isolates could be identified. One of these clusters contained samples of two shedding seasons, indicating persistence on the farm during winter and spring. Repeated measures analysis of variance showed that cows with O157 VTEC infection had higher daily milk production in the period preceding sampling (p = 0.0055). There was no significant association between the results of the LPS-ELISA on serum samples from dairy cows and their O157 status.

Shedding Patterns of Verocytotoxin-ProducingEscherichia coliStrains in a Cohort of Calves and Their Dams on a Scottish Beef Farm

Rectal fecal samples were taken once a week from 49 calves on the same farm. In addition, the dams of the calves were sampled at the time of calf birth and at the end of the study. Strains of verocytotoxin-producing Escherichia coli (VTEC) were isolated from these samples by using PCR and DNA probe hybridization tests and were characterized with respect to serotype, verocytotoxin gene (vtx) type, and the presence of the intimin (eae) and hemolysin (ehxA) genes. A total of 170 VTEC strains were isolated during 21 weeks from 130 (20%) of 664 samples from calves and from 40 (47%) of 86 samples from their dams. The characteristics of the calf strains differed from those strains isolated from the dams with respect to verocytotoxin 2 and the presence of the eae gene. In addition, no calf shed the same VTEC serogroup (excluding O?) as its dam at birth or at the end of the study. The most frequently detected serogroups in calves were serogroup O26 and provisional serogroup E40874 (VTEC O26 was found in 25 calves), whereas in dams serogroup O91 and provisional serogroup E54071 were the most common serogroups. VTEC O26 shedding appeared to be associated with very young calves and declined as the calves aged, whereas VTEC O2 shedding was associated with housing of the animals. VTEC O26 strains from calves were characterized by the presence of the vtx1, eae, and ehxA genes, whereas vtx2 was associated with VTEC O2 and provisional serogroup E40874. The high prevalence of VTEC O26 and of VTEC strains harboring the eae gene in this calf cohort is notable because of the association of the O26 serogroup and the presence of the eae gene with human disease. No association between calf diarrhea and any of the VTEC serogroups was identified.

The serological response to Verocytotoxigenic Escherichia coli in patients with haemolytic uraemic syndrome

To screen sera from 80 patients with clinical haemolytic uraemic syndrome (HUS) and serum antibodies to the lipopolysaccharide (LPS) of Escherichia coli O157, for antibodies to Verocytotoxin-producing Escherichia coli (VTEC) belonging to serogroups O5, O26, O104, O111, O128, O145, O153 and O165. Sera were screened by an LPS-based ELISA and SDS-PAGE/immunoblotting. None of the 80 sera contained antibodies binding to long-chain LPS of any of the LPS types employed; however, nine sera contained antibodies binding to R3 LPS-core epitopes. The presence of patients' serum antibodies to the LPS of E. coli O157, in the absence of antibodies to the LPS of a range of other VTEC, demonstrated that cases of HUS may be caused by strains of O157 VTEC alone and that concurrent infection with multiple strains of VTEC is not a prerequisite for cases of HUS. Antibodies to long-chain LPS of VTEC other than O157 were not detected, and so there was no evidence of infection with VTEC belonging to more than one serogroup. The results of immunoassays such as ELISAs and micro-agglutinations must take into consideration antibodies binding to R3 epitopes located on LPS-core.

Human antibody responses to R3-core epitopes on the lipopolysaccharide of Escherichia coli O157.

To establish the incidence of serum antibodies binding to the R3-core lipopolysaccharide (LPS) of verocytotoxin-producing Escherichia coli (VTEC) O157, in patients with serum antibodies to E. coli O157 LPS, and to characterize the class(es) of antibodies binding to epitopes on the R3-core. SDS-PAGE profiles of LPS prepared from VTEC O157 were used in combination with immunoblotting to detect and characterize serum antibodies binding to the R3-core LPS of VTEC O157. Of 417 sera, referred to the Laboratory of Enteric Pathogens (LEP) for routine O157 serology and found to have serum antibodies to long-chain VTEC O157 LPS, 31 had antibodies binding to the R3-core of VTEC O157 LPS. The majority of the 31 sera contained IgA-class antibodies to both long-chain and R3-core LPS epitopes. Patients who did not develop haemolytic uraemic syndrome (HUS) produced antibodies of the IgM class to R3-core and IgG-class antibodies to long-chain LPS more frequently than patients with HUS. Only 7.4% of sera received by the LEP, and shown to have antibodies to VTEC O157 LPS, contained antibodies binding to the R3-core of VTEC LPS. Most sera contained IgA-class antibodies to both long-chain and R3-core LPS epitopes. Patients infected with VTEC O157 produced antibodies binding to the R3-core epitopes of VTEC O157 LPS only rarely, and these antibodies are unlikely to interfere with the serodiagnosis of infections caused by these organisms.

Survey of Campylobacter species, VTEC O157 and Salmonella species in Swedish wildlife.

Samples collected from 791 wild animals (Canada geese, roe deer, hares, moose, wild boar and gulls) shot during hunting were examined for verocytotoxin-producing Escherichia coli (VTEC) O157, and thermophilic Campylobacter and Salmonella species. With the exception of one positive isolate from a wild boar, VTEC O157 was not isolated from any of the animals. Salmonella species were isolated only from the gulls, of which 4 per cent were estimated to be positive. Thermophilic Campylobacter species were commonly isolated from all the species except deer.