A 1-YEAR STUDY OF ESCHERICHIA-COLI O157 IN CATTLE, SHEEP, PIGS AND POULTRY

Samples of rectal faeces were collected immediately after slaughter fr om 400 cattle each month for a 1-year period and from 1000 each of she ep, pigs and poultry over the same period. Samples were examined for E scherichia coli O157 by enrichment culture in buffered peptone water w ith vancomycin, cefixime and cefsulodin followed by immunomagnetic sep aration and culture of magnetic particles onto cefixime tellurite sorb itol MacConkey agar. E. coli O157 was isolated from 752 (15.7%) of 480 0 cattle, 22 (2.2%) of 1000 sheep and from 4 (0.4%) of 1000 pigs, but not from any of 1000 chickens. Of the cattle sampled, 1840 (38.4%) wer e prime beef animals, 1661 (34.6%) were dairy animals being culled and the status could not be determined for the other 1299 (27%) animals. E. coli O157 was found in 246 (13.4%) of the 1840 beef cattle and 268 (16.1%) of the 1661 dairy cattle. The monthly prevalence of E. coli O1 57 in cattle was 4.8-36.8% and was at its highest in spring and late s ummer. Seventeen of the 22 isolates from sheep were also made over the summer period. All E. coli O157 isolates from sheep and 749 (99.6%) o f the 752 E. coli O157 isolates from cattle were verocytotoxigenic as determined by Vero cell assay and DNA hybridization, eaeA gene positiv e, contained a 92 kb plasmid and were thus typical of strains causing infections in man. In contrast isolates from pigs were non-toxigenic, eaeA gene negative and did not contain a 92 kb plasmid and would, ther efore, be unlikely to be a source of infection for man.