Abstract
Shiga toxin-producing Escherichia coli (STEC) is a foodborne pathogen and known to reside naturally in cattle. The application of untreated biological soil amendments of animal origin on fresh produce fields results in unique food safety challenges. It is critical to identify farm manure management practices to mitigate pre-harvest pathogen contamination. The objective of this study was to quantify the prevalence and level of STEC in cattle manure in the Mid-Atlantic region of the United States. A total of 161 bovine manure samples were collected from 13 cattle farms between 2016 and 2018. The samples were enriched with non-selective and selective media and quantified following a Most-Probable Number (MPN) assay. Among the recovered STEC isolates, PCR was performed to determine the presence of stx, eae, and rfbE. Clermont PCR was performed to identify phylogenetic groups of isolates. Of the 13 farms, 11 had STEC populations between <1.0 and >5.6 log MPN/g. Farm, humidity, and sampling year significantly (p < 0.05) influenced STEC populations in bovine manure. Of the 108 isolates, 50% were stx+ and 14% eae+. Phylogenetic group analysis revealed that 46% of the isolates belonged to group A, 19% to B1, 7% to B2, and 28% to D. Group D had the highest prevalence of stx+ and eae+ and group B1 had the lowest prevalence. Results suggest STEC geographical distribution in the Mid-Atlantic region is farm-specific, and climatic conditions can be critical for its survival and dissemination.