Prevalence of shiga-like-toxin producing Escherichia coli in beef steers and heifers in a slaughter house on Prince Edward Island

Fecal swabs obtained from a random sample of 1000 beef slaughter steers and heifers from 123 different Prince Edward Island (P.E.I.) farms were examined for Shiga-like toxin producing Escherichia coli (SLTEC) using a Vero cell assay (VCA). Multiple isolates from each positive sample were tested similarly. Positive SLTEC colonies were confirmed as E. coli biochemically, tested for drug resistance, serotyped, and examined with monoclonal antibody toxin neutralization and polymerase chain reaction (PCR) techniques to determine the type of toxin. Cattle were classified as positive when a SLTEC isolate was positive on Vero cell assay and toxin production was confirmed by PCR. The prevalence of SLTEC in beef slaughter steers and heifers on P.E.I. was 4% (40/1000) with a confidence interval ranging from 2.3%-5.7% due to the clustering effect of farm. Most SLTEC isolates were sensitive to commonly used antimicrobials. Several SLTEC serotypes recovered in this study are associated with human illness. The most frequently isolated SLTEC serotype was E. coli O157 (5 isolates out of 40). Of these five E. coli O157 serotypes, four were E. coli O157:H7, a serious human pathogen. The types of shiga-like toxins produced by the SLTEC serotypes isolated during the study were identified by specific monoclonal antibodies.

A retail ground beef survey was conducted between June and September 1995 on 200 ground beef samples obtained from grocery stores and meat shops on P.E.I. All samples were tested by VCA for SLTEC and an ELISA test kit developed to identify E. coli O157 antigen in human stool. SLTEC were not detected by VCA. E. coli O157 antigen was detected in four of the samples. (Abstract shortened by UMI.).