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A national outbreak of verotoxin-producing Escherichia coli O157 infection affected five English regions and Wales. Twelve cases were associated with lemon-and-coriander chicken wrap from a single supermarket chain consumed over a 5-day period. An outbreak investigation aimed to identify the source of infection. Descriptive epidemiology and phenotypic and genotypic tests on human isolates indicated a point-source outbreak; a case-control study showed a very strong association between consumption of lemon-and-coriander chicken wrap from the single supermarket chain and being a case (OR 46.40, 95% CI 5.39-infinity, P=0.0002). Testing of raw ingredients, products and faecal samples from staff in the food production unit did not yield any positive results. The outbreak was probably caused by one contaminated batch of an ingredient in the chicken wrap. Even when current best practice is in place, ready-to-eat foods can still be a risk for widespread infection. [ABSTRACT FROM AUTHOR] more...

Objectives: To identify risk factors for transmission of verocytotoxin producing Escherichia coli O157 (VTECO157) and means of prevention.Study Design: Outbreak investigation: retrospective cohort study.Setting: A nursery (child care centre) in North Wales.Subjects: Children attending (n = 104).Methods: Faeces were examined using sorbitol MacConkey agar (SMAC), with cefixime, tellurite, and rhamnose; enrichment in modified tryptone soya broth; and immunomagnetic separation. Symptoms and exposure data were obtained from questionnaires to parents/guardians and children's toiletting and feeding records kept at the nursery.Main Outcome Measure: A "case" was defined as a child with verocytotoxin producing E coli O157 isolated from faeces, or a history of haemolytic uraemic syndrome (HUS) and antibodies to E coli O157 lipopolysaccharide, during the period 10 August to 30 September 1995.Results: The attack rate was 31 in 104. Two children developed HUS. There were higher attack rates among girls and friends who played together. Cases were more likely to attend the nursery more frequently. The mean number of recorded bowel motions/child/half day was 0.51 in cases and 0.21 in well children. Child to staff ratios were high preceding and during the outbreak.Conclusions: A sick child is the most plausible source of infection with subsequent person to person transmission. The record of children's toiletting discriminated between cases and well children and might have allowed earlier detection of the outbreak. This simple record could be considered by other child care facilities as a means of giving early warning of problems with infectious intestinal diseases. [ABSTRACT FROM AUTHOR] more...

The European Union Reference Laboratory (EU-RL) has produced guidelines for a real-time PCR for the detection of verocytotoxigenic Escherichia coli (VTEC). In this study, we validated the EU-RL assay on 545 strains of VTEC and evaluated the utility of the assay for the detection of VTEC from stool specimens. The validation study on cultures showed that the EU-RL VTEC PCR was 99.3% sensitive for the detection of vtx genes; only strains harbouring vtx2f genes were not detected. The assay was 100% sensitive and 100% specific for the detection of both the eae and O157 rfbE genes. In a prospective study involving 500 stool samples, the EU-RL VTEC PCR detected vtx genes in 12.4% of specimens, compared to 3.8% specimens found to be culture-positive for E. coli O157 using the Health Protection Agency national standard culture method. This study showed that the EU-RL VTEC assay was reliable and robust, and an effective rapid screening method for the detection of VTEC from stool specimens. more...

Evidence suggests that frequent and direct exposure to domestic animals has made farmers less susceptible to symptomatic Escherichia coli O157 infection than other members of the community. We have quantified the seroprevalence of antibodies to E. coli O157 lipopolysaccharide (LPS) from a representative cohort of farm workers in three geographically distinct regions of the United Kingdom during two sampling rounds over a 2-year period. All participants completed a questionnaire to determine the range and extent of recent animal contact alongside other potential occupational and environmental exposure routes. A total of 31/946 (3.3%) serum samples contained antibodies to E. coli O157 LPS (from both rounds combined). On the second sampling round, a significant difference in seropositivity was apparent between the three regions, with enhanced seroprevalence linked to recent contact with beef cattle, having a private water supply and contact with a child under 5 years old. Only five seropositive people reported symptoms of a gastrointestinal tract infection, although these symptoms were mild. These results further support the premise of acquired immunity to E. coli O157 associated with prolonged antigenic exposures within the farming environment., (© 2011 Blackwell Verlag GmbH.) more...

At the request of the public health authorities, 31 public amenity premises in England and Wales containing animals of various species were investigated for the presence of verocytotoxigenic Escherichia coli (VTEC) O157 between 1997 and 2007, because of putative associations with human cases. VTEC O157 was confirmed in one or more species on 19 (61.3 per cent) of the premises. There were significant associations between the presence of VTEC O157 and the number of species sampled, the size of the enterprise, the presence of young cattle and the presence of adult pigs. E coli O157 was isolated from 305 (17.8 per cent) of 1715 samples taken from all the premises, and verocytotoxin genes were detected by PCR in 184 (98.4 per cent) of 187 representative isolates. On positive premises, the highest mean proportion of positive samples (29.0 per cent) was in cattle, followed by sheep (24.4 per cent), donkeys (14.6 per cent), pigs (14.3 per cent), horses (12.3 per cent) and goats (9.9 per cent). A high proportion of positive samples was obtained from camelid species sampled on three of the premises. The main phage types (PT) were 2 and 21/28, which were those most commonly isolated from human cases during the same period. A single PT was detected on 14 of the 19 positive premises, with up to six different species having the same PT. more...

Objectives: Uropathogenic and invasive Escherichia coli O25:H4-ST131 isolates producing CTX-M-15 extended-spectrum beta-lactamase (ESBL) enzymes have recently been shown to be disseminated across the globe. In the UK, many CTX-M-15 ESBL-producing E. coli strains have been previously defined as belonging to the epidemic strains A-E, as determined by PFGE. The present study was carried out to define the relationship between these two groups of pathogenic E. coli., Methods: Multilocus sequence typing and PFGE were used for molecular characterization of a collection of 61 ESBL-producing E. coli isolates from across the UK., Results: Strains A to E all belonged to the ST131 clone, further underscoring the epidemiological importance of this lineage., Conclusions: The future spread of the ST131 clone, and its UK variants, should be monitored closely and the pathogenic mechanisms explaining their success should be investigated. more...

Escherichia coli serogroup O26 played an important part in the early work on Verocytotoxin and is an established diarrhoeal pathogen. Recently, Verocytotoxigenic E. coli (VTEC) O26 has been increasingly associated with diarrhoeal disease and frequently linked to outbreaks and cases of haemolytic uraemic syndrome (HUS). This review investigates the pathogenicity, geographical distribution, changing epidemiology, routes of transmission and improved detection of VTEC O26. Laboratory data on VTEC O26 isolates and clinical data on HUS suggest a true difference in the incidence of VTEC O26 in different geographic locations. However, few diagnostic laboratories use molecular methods to detect VTEC and so it is difficult to assess the role of VTEC O26 in causing diarrhoeal disease. VTEC O26 is frequently found in the cattle population but rarely in food. However, the small number of outbreaks analysed to date are thought to be food-borne rather than associated with direct or indirect contact with livestock or their faeces. The increase in awareness of VTEC O26 in the clinical and veterinary setting has coincided with the development of novel techniques that have improved our ability to detect and characterize this pathogen. more...

The aim of this study was to compare genotypic characteristics seen in typical EAggEC isolated during a study of intestinal infectious disease from cases and controls, and to identify which genes, or combinations of genes, were most associated with diarrhoeal disease. We also investigated the association of genotype with certain characteristics, such as presence of fimbrial genes and adherence to Hep-2 cells. The aafC gene, encoding the usher for AAFII, was the only gene significantly associated with patients with diarrhoea (P < 0.005), and the aggC gene, which encodes the usher for AAFI, was the only gene significantly associated with the healthy control group (P < 0.002). Putative virulence genes significantly associated with aggregative adherence included aafC, aggR, pet, pic and astA. The shf, pet and astA genes were all more likely to be associated with type II fimbriae than with type I. We conclude that in addition to presence and absence of certain genes, studies of EAggEC pathogenicity should investigate the combinations and associations of putative virulence factors. more...

The aim of this study was to assess the usefulness of a multiplex PCR assay targeting the aat, aaiA and astA genes for the detection of typical and atypical enteroaggregative Escherichia coli (EAEC) in bacterial cultures from faecal samples from patients with community-acquired diarrhoea. The isolates harbouring these genes were also tested using the HEp-2 cell-adhesion assay to clarify their EAEC status. aat, aai or astA was found in E. coli faecal isolates from 39 (7.8 %) of 500 patients, and 20 of these strains adhered to HEp-2 cells in a pattern characteristic of EAEC. Eight isolates carrying the aai or astA gene but not the aat gene were shown to be HEp-2 cell test positive, although 12 strains with this genotype were HEp-2 cell test negative. Using the HEp-2 adhesion assay as the gold standard, the addition of primers detecting aaiA and astA to the aat PCR increased the number of EAEC isolates detected, but identified strains of E. coli that were not EAEC. The variety of genotypes exhibiting aggregative adherence highlights the problems associated with developing a molecular diagnostic test for EAEC. This PCR assay detects a variety of strains exhibiting characteristics of the EAEC group, making it a useful tool for identifying both typical and atypical EAEC. more...

Enteroaggregative Escherichia coli (EAggEC) is an important cause of diarrhea worldwide, and there is a need for better detection methods in diagnostic laboratories. The aims of this study were i) to characterize strains of EAggEC by assigning each isolate a genotypic profile and (ii) to determine target genes for the detection of both typical and atypical EAggEC. The heterogeneity of the EAggEC group makes selection of a single target gene difficult. The plasmid-encoded genes, aat, aggR, and aap, are all appropriate targets for the detection of typical EAggEC. Of the chromosomally encoded genes, aaiA would be the most suitable target gene to identify typical and atypical EAggEC. The astA gene, encoding the enteroaggregative heat stable toxin, although not specific for EAggEC, may be used effectively in combination with other specific EAggEC genes. A polymerase chain reaction test based on the detection of characteristic EAggEC virulence genes, such as aat, astA, and aaiA, would improve EAggEC diagnosis. more...

The aim of this study was to characterise the atypical enteropathogenic Escherichia coli (EPEC) strains isolated during a study of intestinal infectious disease in the UK by serotyping, intimin subtyping, and antimicrobial resistance typing. Serotypes, intimin subtypes, and resistance patterns of strains from cases were then compared with those from the control group. A wide range of serotypes, intimin subtypes, and antimicrobial resistance patterns was identified in isolates from both cases and controls, with O70:H11 and O111:H- being the most frequently detected serotypes. The most common intimin types were gamma and gamma(2). Thirty-six percent of the EPEC isolates were resistant to at least one antimicrobial agent. No significant differences in the characteristics of EPEC strains isolated from patients with symptoms of gastrointestinal disease versus those isolated from healthy controls were detected, although strains harbouring the beta-intimin subtype were more commonly isolated from children under 5 years of age (p=0.002). The compilation of data on atypical EPEC strains presented here indicates the need for further study of their virulence and epidemiology in order to assess their significance as human pathogens. more...

A DNA microarray was used to analyze the distribution of plasmid and chromosomal genes among strains of enteroaggregative Escherichia coli (EAEC) isolated from a prospective diarrhoea surveillance study in the United Kingdom. Target genes were extracted from existing databases and from the genome sequence of prototype EAEC strain 042. We found that strains exhibiting the aggregative adherence (AA) phenotype could be broadly divided into two groups depending upon whether they harboured genes from the EAEC virulence plasmid (pAA) and a set of chromosomal genes found in EAEC strain 042. Several chromosomal loci were inherited en bloc, and were more common in strains which we designated Group 1; genes at the pheU locus were particularly conserved. Genes encoded on the pAA plasmid and those under control of the master regulator AggR were also concentrated in the Group 1 EAEC. A gene encoding a type 1 pilin allele was detected more frequently in Group 2 EAEC. Our data suggest that strains previously designated as typical EAEC harbour a large number of conserved plasmid and chromosomal loci, further illuminating a package of virulence genes common to the most important EAEC. more...

We conducted prospective surveillance of childhood hemolytic uremic syndrome (HUS) from 1997 to 2001 to describe disease incidence and clinical, epidemiologic and microbiologic characteristics. We compared our findings, where possible, with those of a previous study conducted from 1985 to 1988. The average annual incidence of HUS for the United Kingdom and Ireland (0.71/100,000) was unchanged from 1985 to 1988. The overall early mortality had halved, but the reduction in mortality was almost entirely accounted for by improved outcome in patients with diarrhea-associated HUS. The principal infective cause of diarrhea-associated HUS was Shiga toxin-producing Escherichia coli O157 (STEC O157), although in the 1997-2001 survey STEC O157 phage type (PT) 21/28 had replaced STEC O157 PT2 as the predominant PT. The risk of developing diarrhea-associated HUS was significantly higher in children infected with STEC O157 PT 2 and PT 21/28 compared with other PTs. Hypertension as a complication of HUS was greatly reduced in patients with diarrhea-associated HUS. more...

Verocytotoxin-producing Escherichia coli (VTEC) causes a wide spectrum of disease in humans, from mild diarrhoea to haemolytic uraemic syndrome (HUS). The verocytotoxin (vtx) and intimin (eae) genes of VTEC strains, other than those of serogroup O157, were subtyped to identify common properties that may be associated with increased pathogenicity. Strains were isolated from patients with HUS, those with diarrhoea or from asymptomatic individuals. Strains of VTEC that carried vtx(2) gene subtypes vtx(2) and vtx(2c) were most commonly associated with HUS, whereas strains from patients with less severe disease and from the healthy control group were more likely to have vtx(1c) or vtx(2d) genes. The eae gene was detected more frequently in strains isolated from HUS patients than in those associated with cases of diarrhoea; beta-intimin was the most common intimin subtype in strains isolated from both groups of patients. None of the strains from the healthy control group carried the eae gene. more...

During the decade to 1999, the incidence of human infections with the zoonotic pathogen verocytotoxin-producing Escherichia coli O157 (VTEC O157) increased in England and Wales. This paper describes the results of a survey of 75 farms to determine the prevalence of faecal excretion of VTEC O157 by cattle, its primary reservoir host, in England and Wales. Faecal samples were collected from 4663 cattle between June and December 1999. The prevalence of excretion by individual cattle was 4.2 per cent (95 per cent confidence interval [CI] 2.0 to 6.4) and 10.3 per cent (95 per cent CI 5.8 to 14.8) among animals in infected herds. The within-herd prevalence on positive farms ranged from 1.1 to 51.4 per cent. At least one positive animal was identified on 29 (38.7 per cent; 95 per cent CI 28.1 to 50.4) of the farms, including dairy, suckler and fattening herds. The prevalence of excretion was least in the calves under two months of age, peaked in the calves aged between two and six months and declined thereafter. The phage types identified most widely were 4, 34 and 2, which were each found on six of the 29 positive farms. more...

PCR-RFLP methods for subtyping the intimin gene from strains of typical and atypical enteropathogenic Escherichia coli (EPEC) and Verocytotoxin-producing E. coli (VTEC) were compared. A novel HhaI PCR-RFLP method was developed that was rapid, easy to use and amplified an 1852 bp fragment of the intimin gene from all isolates examined. This method was used to investigate the intimin sub-types of EPEC strains associated with 14 outbreaks of diarrhoeal disease between 1967 and 2001, and 20 sporadic cases between January and December 2000, in the UK and Eire. In this study, genes encoding alpha, beta, gamma, delta and zeta-intimin were detected in the EPEC strains associated with outbreaks and beta, gamma, epsilon, theta and zeta-intimin genes were identified in isolates from sporadic cases. The beta-intimin gene was the most frequently detected sub-type in both the outbreak and sporadic strains. more...

The salivary antibody response to the Escherichia coli O157 LPS antigen was assessed in 44 patients with serum antibodies binding to the LPS of E. coli O157. Saliva from 477 controls was also examined to assess the specificity of the immunoassay used. Twenty of the 44 patients had salivary antibodies to E. coli O157 LPS, giving the salivary antibody test a sensitivity of 0.45 and a predictive positive value for seropositivity of 1.00. The presence of these antibodies appeared not to relate to the time interval between serum sampling and saliva sampling. None of the 477 volunteers had salivary antibodies binding to the LPS of E. coli O157 alone; however, 15 had antibodies which bound non-specifically to both O157 LPS and BSA. more...

Aims: To investigate subtyping methods for verocytotoxin-producing Escherichia coli (VTEC) O128ab:H2., Methods and Results: Eleven human and food strains isolated over a 15-year period were examined. All were intimin (eae)-negative, but all possessed enterohaemolysin and VT1-encoding sequences which in nine strains were vtx1c variant. Ten strains had VT2 genes which were all vtx2d. Plasmid profiles and randomly amplified polymorphic DNA-PCR were not discriminatory. Long-PCR restriction fragment length polymorphism of amplicons bound by the p gene and the VT2A subunit had screening potential. Pulsed field gel electrophoresis (PFGE) using XbaI gave fine discrimination although VT2 sequences were located on a 220 kbp fragment conserved in nine strains and on a 200 kbp fragment in the 10th., Conclusions: As a result of apparent clonality, PFGE proved essential for differentiation. Long-PCR has promise for screening but requires further evaluation of inter-strain variable sequences., Significance and Impact of the Study: A combined phenotypic and genotypic screen, and PFGE for selected strains was effective. more...

Antibody-antigen cross-reactions were examined with sera from patients with Escherichia coli O157 infection and lipopolysaccharide (LPS) purified from a range of enterohaemorrhagic E. coli (EHEC) including those belonging to serogroups O26, O103, O111, O145 and O157. Six of 10 patients infected with an O157 EHEC produced serum antibodies that cross-reacted with common LPS-core epitopes, which were expressed by 23 of 33 strains of EHEC examined. These common LPS-core epitopes were also present on strains of E. coli O26 which did not produce verocytotoxin. These cross-reacting antibodies did not influence the basic immunoblotting procedures used for the routine serodiagnosis of infections with E. coli O157. more...

Shiga toxin (Verocytotoxin) producing E. coli (STEC) O157 were isolated from 168 patients living in different parts of Germany. Most isolates were from sporadic cases and seven small outbreaks with STEC O157 were identified. The 168 strains were examined for phenotypic and genotypical traits in order to identify major types of STEC O157 occurring in Germany. Phage typing (PT) revealed PT8 (n = 54) and PT2 (n = 48) strains as most frequent (60.7%) among the isolates. Carriage of the stx(2) gene by STEC O157 was closely associated with hemolytic uremic syndrome (100%) and with bloody diarrhea (61.7%). The stx(2) gene was frequent in PT88, PT47 (both 100%), PT2 (91.5%) and PT4 (87.5%) strains and more rarely (33.3%) found in strains belonging to the other PTs. PT8 and PT2 strains formed two groups which differed from each other in their motility, stx-genotypes and the severity of the illness they caused. Pulsed-field gel electrophoresis of PT2 and PT8 strains and hybridization of XbaI digested DNA with stx(1) and stx(2) specific gene probes revealed similarities among epidemiologically unrelated strains belonging to the same PT. The results indicate that STEC O157 PT2 and PT8 strains form two distinct subclones which are dominating in Germany and other European countries. more...

A 12-month abattoir survey was conducted between January 1999 and January 2000, to determine the prevalence of faecal carriage of verocytotoxin-producing Escherichia coli O157 (VTEC O157) in cattle and sheep slaughtered for human consumption in Great Britain. Samples of rectum containing faeces were collected from 3939 cattle and 4171 sheep at 118 abattoirs, in numbers proportional to the throughput of the premises. The annual prevalence of faecal carriage of VTEC O157 was 4.7 per cent (95 per cent confidence interval 4.1 to 5.4) for cattle and 1.7 per cent (1.3 to 2.1) for sheep, values which were statistically significantly different from each other (P < 0.001). The organisms were recovered from both cattle and sheep slaughtered throughout the year and at abattoirs in all regions of the country, but the highest prevalence was in the summer. The most frequency recovered VTEC O157 isolates were phage types 2, 8 and 21/28 in cattle and 4 and 32 in sheep, the five most frequently isolated phage types associated with illness in people in Great Britain during the same period. more...

An investigation of infectious intestinal disease in England included examination of feces for Vero cytotoxin-producing Escherichia coli (VTEC). Using DNA probe hybridization 27 VTEC strains were identified, 12 were from cases, and of these three belonged to serogroup O157. The remaining 15 strains were isolated from controls. The strains were confirmed biochemically as E. coli, they were serotyped and characterized according to their toxin production, the presence of sequences encoding intimin (eae) and enterohemolysin was determined and resistance to antimicrobial agents was determined. Six of the nine cases with non-O157 VTEC were less than 16 years old, only two of the 15 controls were under 16. Infection with more than one micro-organism was also considered. more...

Aims: Strains of Verocytotoxin-producing Escherichia coli (VTEC) from Scottish beef cattle on the same farm were isolated during four visits over a period of eight months. Characteristics of these strains were examined to allow comparisons with strains of VTEC associated with human infection., Methods and Results: Strains were characterized to investigate the relationship between these bovine isolates with respect to serotype, Verocytotoxin (VT) type, intimin-type, and presence or absence of the enterohaemolysin genes. VT genes were detected in 176 of 710 (25%) faecal samples tested using PCR, although only 94 (13%) VTEC strains were isolated using DNA probes on cultures. Forty-five different serotypes were detected. Commonly isolated serotypes included O128ab:H8, O26:H11 and O113:H21. VTEC O26:H11 and O113:H21 have been associated with human disease. Strains harbouring the VT2 genes were most frequently isolated during the first three visits to the farm and those with both VT1 and VT2 genes were the major type during the final visit. Of the 94 strains of non-O157 VTEC isolated, 16 (17%) had the intimin gene; nine had the gene encoding beta-intimin and seven strains had an eta/zeta-intimin gene. Forty-one (44%) of 94 strains carried enterohaemolysin genes., Conclusions: Different serotypes and certain transmissible characteristics, such as VT-type and the enterohaemolysin phenotype, appeared to be common throughout the VTEC population at different times., Significance and Impact of the Study: Detailed typing and subtyping strains of VTEC as described in this study may improve our understanding of the relationship between bovine VTEC and those found in the human population. more...

A marked increase in sporadic cases of enteritis due to enterohemorrhagic Escherichia coli serogroup O157 occurred in Osaka City, Japan, during 1996. To elucidate why the number of cases had increased, the isolates were classified using phage typing, random amplified polymorphic DNA analysis, and pulsed-field gel electrophoresis (PFGE). Fifty-seven percent of the isolates (105/184) belonged to the same phage type (PT-32) and gave the same PFGE pattern; the clone had been isolated during a 3-week period, with a peak on July 15. It was concluded that the majority of the cases identified in July 1996 formed an outbreak, although epidemiological links to a possible common source were not established. The possibility that this outbreak was part of a huge regional outbreak including children at primary schools in Sakai City was discussed. more...

Background: A hospital-based study was performed to (1) compare phenotypic and genotypic diagnostic tests for enteropathogenic Escherichia coli, enteroaggregative E. coli, and diffuse-adhering E. coli (collectively termed adherent E. coli) and (2) to assess the importance of these different classes of adherent E. coli as causes of infant diarrhea in the United Kingdom in comparison with other enteropathogens., Methods: E. coli isolated from 1,496 infants with diarrheal disease and from 546 age-related controls were screened for enteropathogenic E. coli, enteroaggregative E. coli, and diffuse-adhering E. coli using HEp-2 cell adherence assays and DNA probes., Results: Marked discrepancies between the phenotype and genotype of isolates indicate significant heterogeneity among enteroaggregative E. coli and diffuse-adhering E. coli strains. Depending on the assay used, adherent E. coli were isolated as the only putative pathogen in 23% to 27% of diarrhea cases, a significantly higher incidence than in the control group. Individually, enteroaggregative E. coli (8.5-8.6% of cases) and diffuse-adhering E. coli (10.4-11.3% of cases), but not enteropathogenic E. coli (4.5-7.5% of cases), were significantly associated with diarrhea., Conclusions: These studies indicate that adherent E. coli may be an important cause of diarrhea in infants in the United Kingdom; they also emphasize the need for more specific virulence-based tests for these putative classes of "diarrheagenic" (diarrhea causing) E. coli. more...

Aims: To compare an experimental Reversed-Passive Latex Agglutination (RPLA) with Vero cells for the detection of Verocytotoxin expressed by VT-producing strains of Escherichia coli (VTEC)., Methods and Results: The RPLA was used alongside a Vero cell tissue culture assay for the detection of VT in bacterial culture supernatant fluids and patients' faecal extracts., Conclusion: The RPLA was comparable with the Vero cell assay, although slightly less sensitive., Significance and Impact of the Study: The RPLA test proved to be a simple, rapid and convenient method of detecting VT in bacterial culture supernatant fluids and in the faeces of patients infected with VTEC. more...

Transmission of verocytotoxin (VT)-producing Escherichia coli (VTEC) occurs by three main routes. These comprise food- or water-borne infections, acquisition of disease by direct or indirect contact with animals and person-to-person spread. Phenotypic typing of VTEC belonging to serogroup O157 is achieved by phage typing and identification of VT type. These properties quickly provide evidence for the linkage of human cases and their association to potential sources. DNA-based subtyping methods such as pulsed field gel electrophoresis (PFGE) are generally required to increase discrimination of VTEC O157 strains so that the spread of specific strains can be monitored. Phenotypic and DNA-based methods were used in the investigation of 85 general outbreaks of VTEC O157 infection between 1995 and 1999. Results were used in conjunction with epidemiological data to provide direct or indirect evidence for the likely route of transmission. Detailed strain fingerprinting identified specific food vehicles and reservoirs of infection in animals. Typing supported the implementation of measures to control the spread of infection that included pasteurisation orders, product withdrawal, temporary closure of retail premises and open farms and the introduction of HACCP-based working practices. In outbreaks involving widely distributed foods, DNA-based examination of apparently sporadic isolates with the same phage and VT type as outbreak strains was performed to identify additional potential outbreak cases and estimate the spread of infection. Strain typing was applied in outbreaks in nurseries and other institutions to monitor person-to-person spread, including careers and their families and to assess the involvement of community cases occurring at the same time. Rapid exchange of epidemiological, microbiological and typing data will be increasingly important in investigation of VTEC O157 outbreaks. more...

A total of 3429 isolations of verocytotoxin-producing Escherichia coli O157 (VTEC O157) was confirmed from human sources in England and Wales during the period 1995-1998. The largest annual total was 1087 in 1997. Most infections occurred in the third quarter of each year. The overall rate of infection ranged from 1.28 to 2.10/100,000 population and showed regional variation. The highest incidence was in children aged 1-4 years. Annually, between 5% and 11% of strains were from patients who had travelled abroad. There were 67 general outbreaks of infection represented by 407 (11.9%) VTEC O157 isolates. Outbreaks involved transmission by contaminated food or water, person-to-person spread and direct or indirect animal contact, and five were associated with foreign travel. The majority (76%) of strains carried verocytotoxin (VT) 2 genes and 23.3% were VT1+VT2. Most strains had the flagellar antigen H7, but c. 14% were non-motile. Approximately 20% of isolates were resistant to antimicrobial agents, predominantly streptomycin, sulphonamides and tetracycline. In addition to VTEC O157, strains of serogroup O157 that did not possess VT genes were identified. These were either derivatives of VTEC O157 that had lost VT genes or were strains with H antigens other than H7 that have never been associated with VT production. Strains of VTEC other than O157 were characterised. Most were associated with diarrhoea, bloody diarrhoea or haemolytic uraemic syndrome and had virulence markers in addition to VT. more...

Since the early 1990s there has been a dramatic increase in resistance to antimicrobial drugs in Salmonella enterica and Campylobacter spp., and to a lesser extent in Vero cytotoxin-producing Escherichia coli O157 from cases of human infection in developed countries. For S. Typhimurium a particularly important aspect of this increase has been the widespread dissemination of a multiply drug-resistant (MR) strain of definitive phage type (DT) 104 in food animals since the early 1990s. The use of antimicrobials for prophylaxis in food producing animals has been an important factor in the emergence of strains with resistance to certain antimicrobials. It is hoped that recently introduced Codes of Practice for the prophylactic use of antimicrobials in food animals will result in a decline in the occurrence of drug resistant strains in the food chain. more...

Verocytotoxin-producing Escherichia coli (VTEC) O157 phage type 2 (PT2) was isolated from three calves and two goats on a farm open to the public. Phenotypic and DNA-based typing showed that the strains were identical or very closely related to those obtained from an outbreak of VTEC O157 infection in two separate family groups who visited the farm. No VTEC O157 PT2 was isolated again from the farm during a 12-month longitudinal bacteriological study undertaken after the infected animals had been removed. However, phenotypically and genotypically indistinguishable VTEC O157 PT2/28 strains were detected in two of 474 faecal samples collected at monthly visits from 15 species of animals of various ages. The two isolates were obtained from calves from different sources sampled 146 days apart, suggesting that the infection had persisted on the farm although it was not detected in the other species. The same strain was subsequently isolated from another calf housed in the same pen as one of the infected calves. The longest period during which the organism was excreted was seven days. No VTEC O157 was isolated either from 204 replacement animals (including 138 orphan lambs and 10 calves) brought in from various sources, and sampled while they were kept in isolation for two weeks before being introduced to the farm, or from environmental samples. During the study a visitor became ill with VTEC O157 PT2. However, the isolate was distinct from those recovered from the farm and there was no evidence to suggest that the visit was the source of the infection. more...

Since 1990 there have been dramatic increase in the occurrence multiply drug-resistant strains of zoonotic pathogens causing infections in humans in many developed countries. Of particular note has been the epidemic spread of MR strains of S. typhimurium DT 104, which now appear to have an almost world-wide distribution. Within DT104 the increasing spectrum of resistance is of considerable concern, with strains with decreased susceptibility to ciprofloxacin increasing in incidence in the United Kingdom and also causing serious disease in humans in other countries. For campylobacters the incidence of ciprofloxacin-resistant organisms is also increasing, with reports of such isolates from numerous countries throughout the world. For VTEC O157, although resistance is increasing, multiple resistance and resistance to ciprofloxacin remains rare. Drug resistance in food-borne pathogens is an unfortunate but almost inevitable consequence of the use of antimicrobials in food animals. Although for some pathogens--e.g., Campylobacter spp., the use of antimicrobials in human medicine is also an important factor (Smith el al 1999), it is the use of antimicrobials in food animals which has been a major factor in the development of decreased susceptibility to antibiotics such as ciprofloxacin in zoonotically-transmitted salmonellas. Such use is quite legitimate. However it is regrettable that recommendations such as propounded in 1992 in the UK by the Expert Group on Animal Feedingstuffs--the Lamming Committee, that any new antibiotics with cross resistance to those used in human medicine should not be used for prophylaxis in animal husbandry, were not accepted (Anonymous, 1992). Although the clock cannot be turned back, to combat the development of resistance to such important drugs as the fluoroquinolones it is hoped that a Code of Practice for their use in food animals will soon be internationally implemented. more...

A study of Vero cytotoxin producing Escherichia coli (VTEC) O157 infections in Cornwall and West Devon was conducted to identify associations between human infection and contact with farm animals. In three years from November 1994 to October 1997, 63,000 stool specimens were submitted to four participating microbiology laboratories and screened for E. coli O157. Sixty-nine confirmed cases were interviewed to assess the extent of any direct or indirect contact with farm animals. Nine out of 22 investigations conducted on farms--in which animal rectal swabs, faecal specimens, fore-stream milk samples (first draw-off from teats), and various environmental samples were tested--yielded VTEC O157. In seven incidents one or more isolates from animals were indistinguishable from the isolate(s) from the human case(s) using phenotypic and genotypic subtyping. Cases associated with animal contact included farm visitors, holidaymakers, and members of farming families and farm workers. more...

Population-based surveillance for Vero cytotoxin-producing Escherichia coli (VTEC) O157 has been carried out in Wales since 1990. The annual incidence has remained stable during the 9-year period (mean: 1.6 cases per 100,000 population); the rate is highest in children younger than 5 years of age. Blood in the stool is reported in fewer than half the cases, indicating the importance of screening all fecal specimens for VTEC O157. more...

Three children, one who lived on an open farm and two who visited the farm in school parties, developed Vero cytotoxin producing Escherichia coli (VTEC) O157 infection in 1997. All had been in direct contact with animals. All were admitted to hospital with diarrhoea and two developed the haemolytic uraemic syndrome, one of whom developed severe neurological impairment. E.coli O157 phage type 21 that produced Vero cytotoxin 2 were isolated from the three children and from a goat paddock and two cows at the farm. The isolates were indistinguishable by molecular typing. The farm closed voluntarily for six weeks while recommendations to reduce the exposure of visitors to faecal contamination and to improve hygiene procedures (especially handwashing) were implemented. More research is needed into all aspects of VTEC O157 on farms, including the natural history of carriage in animals, the organism prevalence and factors that affect infectivity to humans. Further consideration is needed about the role of open farms in zoonoses, and how open farms can be assisted in reducing risks for visitors. The public need to be educated about the risks and about their responsibilities, which include the need to wash hands thoroughly and to avoid hand to mouth contact when visiting farms. more...

Vero cytotoxin-producing Escherichia coli O157 belonging to four phage types (PTs) caused 11 outbreaks of infection in England and Wales in 1995. Outbreak strains of different PTs were distinguishable by DNA-based methods. Pulsed-field gel electrophoresis best discriminated among strains belonging to the same PT, distinguishing six of the seven PT2 outbreak strains and both PT49 outbreak strains. more...

The genes encoding the CS6 colonization factor were cloned from two human enterotoxigenic Escherichia coli strains of different serotypes. The DNA sequences from both clones were nearly identical and contained four open reading frames. Two of them have homology to genes encoding molecular chaperones and ushers found in many other operons encoding colonization factors. The two remaining open reading frames encode two heterologous major subunit proteins which makes CS6 unique because other colonization factors have only one major subunit. Upstream and downstream of the CS6 operon the DNA sequences of the clones diverged abruptly. more...

Nine hundred and twenty-five Escherichia coli isolates from cases of diarrhoea in the United Kingdom and belonging to enteropathogenic E. coli (EPEC) O serogroups were examined for virulence properties. The tests included adhesion to HEp-2 cells, the fluorescence actin staining (FAS) test (which correlates with the ability to cause attaching and effacing lesions) and DNA hybridisations with probes to detect sequences for eaeA (E. coli attaching and effacing factor), EAF (EPEC adherence factor), verocytotoxins VT1 and VT2, enteroaggregative E. coli and diffusely adherent E. coli. The O serogroups examined were 18, 26, 44, 55, 86, 111, 114, 119, 125, 126, 127, 128 and 142. Six hundred and sixty strains (71.4%) hybridised with at least one of the DNA probes. Over 80% of strains in O serogroups 26, 55, 119, 125, 127 and 142 and 41% of strains of serogroups 86, 111, 114, 126 and 128 hybridised with the eae probe and most showed localised attachment and were FAS-positive. However, <10% of these eae probe-positive strains hybridised with the EAF probe. Eighty-four of 232 strains in O serogroups 44, 86, 111, and 126 were enteroaggregative. VT genes were detected in 57 of 402 strains in O serogroups 26, 55, 111 and 128. Identification of EPEC by serogrouping was shown to be an effective method of identifying strains with pathogenic potential, although the organisms were diverse in their properties. more...

Specimens from 181 patients with diarrhoea were examined by a Military General Hospital in a 3-month period during deployment of troops to Saudi Arabia in 1990/1. DNA probes for heat labile (LT) and heat stable (ST) enterotoxin genes identified enterotoxigenic Escherichia coli (ETEC) in 47 of the specimens (26%) and 49 ETEC strains were isolated. The majority (55%) belonged to a novel ETEC serotype having the O-antigen 159 and a flagellar antigen designated as a provisional new type. They produced ST and the coli surface associated antigen (CS)6. Strains of serotype O6:H16 represented 22% of the ETEC examined. They produced ST, LT and CS3 together with either CS1 or CS2. The remaining ETEC belonged to seven O:H serotypes. Overall, ST was the only enterotoxin gene identified in 73% of the ETEC and 67% of the strains expressed CS6 in the absence of other colonization antigens. Resistance to three or more antibiotics was observed in 53% of the ETEC, including most of the O159 strains. more...