EPIDEMIOLOGY OF ESCHERICHIA-COLI O157 IN FEEDLOT CATTLE

Fecal samples from cattle in 100 feedlots in 13 states were bacteriolo gically cultured for Escherichia coil O157 that did not ferment sorbit ol, lacked beta-glucuronidase. and possessed genes coding for Shiga-li ke toxin. In each feedlot 30 fresh fecal-pat samples were collected fr om each of four pens: with the cattle shortest on feed, with cattle lo ngest on feed, and with cattle in two randomly selected pens. E. coli O157 was isolated from 210(1.8%) of 11.881 fecal samples. One or more samples were positive for E. coli O157 in 63 of the 100 feedlots teste d, E. coil O157 was found at roughly equal prevalence in all the geogr aphical regions sampled. The prevalence of E. coli O157 in the pens wi th cattle shortest on feed was approximately threefold higher than for randomly selected and longest on feed pens. Of the E. coil O157 isola tes found in this study, 89.52% expressed the H7 flagellar antigen. E. coli O157 was found to be widely distributed among feedlot cattle, bu t at a low prevalence, in the United States.