Pre-slaughter handling of cattle and Shiga toxin-producing Escherichia coli (STEC)

Aims: The aim of the study was to monitor the shedding and transmission of generic and Shiga toxin-producing Escherichia coli (STEC) in a consignment of cattle during lot feeding. Methods and Results: Faecal and environmental samples were tested for total E. coli and screened with PCR specific for Shiga toxin and O157 rf6. STEC were isolated using colony hybridization and characterized by serology and genotyping. STEC prevalence initially decreased after the diet shift from p asture to grain, although there were intermittent peaks in numbers of cattl e shedding STEC and E. coli O157. Water troughs and soil were intermittentl y contaminated. Common genotypes and serotypes were isolated from animals, water and soil in the feedlot, with additional types introduced at slaughte r. Conclusions: STEC and E. coli O157 are endemic in cattle and intermittent p eaks in shedding occur. Prevention of these peaks and/or reduction in trans mission is required to reduce the risk of carcass contamination during slau ghter. Significance and Impact of the Study: These findings contribute to the unde rstanding of the ecology of STEC and suggest control points for reducing ST EC contamination in feedlot cattle production.