A total of 3429 isolations of verocytotoxin-producing Escherichia coli O157 (VTEC O157) was con®rmed 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-toperson spread and direct or indirect animal contact, and ®ve 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¯agellar 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 identi®ed. 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.

In a survey of wild birds (mainly gulls), 0·9% of the bacterial isolates from faecal samples at an urban landfill site and 2·9% of bacterial isolates from faecal samples on intertidal sediments in Morecambe Bay were Vero cytotoxin‐producing Escherichia coli O157. Isolation procedures employing commonly used cultural methods were hindered by the selection of a large number of false positives. The only procedure which resulted in the isolation of E. coli O157 from bird faecal samples was : enrichment (18 h) in a selective tryptone soya broth followed by filtration using hydrophobic grid membranes and growth on Chromagar®O157. The majority of isolates selected as potential E. coli O157 by characteristic growth on Chromagar®O157 could be eliminated by subsequent growth on CT‐SMAC or CR‐SMAC. This second identification (characterization) stage reduced the number of potential E. coli O157 requiring further confirmation by typing methods (serotype and Vero cytotoxin) by more than 70%.

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.

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This study investigated the shedding of Escherichia coli O26, O103, O111, O145, and O157 in a cohort of beef calves from birth over a 5-month period and assessed the relationship between shedding in calves and shedding in their dams, the relationship between shedding and scouring in calves, and the effect of housing on shedding in calves. Fecal samples were tested by immunomagnetic separation and by PCR and DNA hybridization assays. E. coli O26 was shed by 94% of calves. Over 90% of E. coli O26 isolates carried the vtx 1 , eae, and ehl genes, 6.5% carried vtx 1 and vtx 2 , and one isolate carried vtx 2 only. Serogroup O26 isolates comprised seven pulsed-field gel electrophoresis (PFGE) patterns but were dominated by one pattern which represented 85.7% of isolates. E. coli O103 was shed by 51% of calves. Forty-eight percent of E. coli O103 isolates carried eae and ehl, 2% carried vtx 2 , and none carried vtx 1 . Serogroup O103 isolates comprised 10 PFGE patterns and were dominated by two patterns representing 62.5% of isolates. Shedding of E. coli O145 and O157 was rare. All serogroup O145 isolates carried eae, but none carried vtx 1 or vtx 2 . All but one serogroup O157 isolate carried vtx 2 , eae, and ehl. E. coli O111 was not detected. In most calves, the temporal pattern of E. coli O26 and O103 shedding was random. E. coli O26 was detected in three times as many samples as E. coli O103, and the rate at which calves began shedding E. coli O26 for the first time was five times greater than that for E. coli O103. For E. coli O26, O103, and O157, there was no association between shedding by calves and shedding by dams within 1 week of birth. For E. coli O26 and O103, there was no association between shedding and scouring, and there was no significant change in shedding following housing.