Verocytotoxin-producing Escherichia coli (VTEC) O157 and other VTEC from human infections in England and Wales: 1995-1998

A total of 3429 isolations of verocytotoxin-producing Escherichia coli O157 (VTEC O157) was confirmed from human sources in England and Wales during t he period 1995-1998, The largest annual total was 1087 in 1997, Most infect ions occurred in the third quarter of each year, The overall rate of infect ion ranged from 1.28 to 2.10/100000 population and showed regional variatio n. 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 we re 67 general outbreaks of infection represented by 407 (11.9%) VTEC O157 i solates. Outbreaks involved transmission by contaminated food or water, per son-to-person spread and direct or indirect animal contact, and five were a ssociated with foreign travel. The majority (76%) of strains carried verocy totoxin (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, sulphonamid es and tetracycline. In addition to VTEC O157, strains of serogroup O157 th at 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 t han H7 that have never been associated with VT production, Strains of VTEC other than O157 were characterised, Most were associated with diarrhoea, bl oody diarrhoea or haemolytic uraemic syndrome and had virulence markers in addition to VT.