Prevalence of Escherichia coli and Salmonella in Runoff of Two Cattle Feedlots in North Dakota

Livestock waste is used extensively as manure in crop farming. Improperly managed manure can contaminate foods such as raw produce and can serve as a major source of zoonotic foodborne pathogens such as Escherichia coli and Salmonella. The objective of this study was to detect and estimate the prevalence of E. coli (O157 and non-O157) serotypes and Salmonella species in runoff samples collected from two cattle feedlots (A and B) in North Dakota. Runoff samples were collected using automatic samplers (ISCO 6712) and processed by following standard culture and confirmatory methods for the isolation of E. coli and Salmonella. Of 136 samples collected from feedlots A and B, 106 (78%) tested positive for at least one of the E. coli serotypes (O26, O45, O103, O111, O113, O121, O145 and O157), and 54 (40%) tested positive for Salmonella. One to seven E. coli serotypes were detected in each of the positive runoff samples, and a total of 237 E. coli serotypes were detected in the 106 positive runoff samples. Of the 237 serotypes, the most frequent was O45 (22%), followed by O103 (19%), O157 (18%), O121 (15%), O26 (9%), O111 (5%), O113 (5%), and O145 (5%). The number of serotypes recovered from feedlot A (169/237) was higher (P < 0.001) than the number recovered from B (68/237). These data provide evidence of the presence of E. coli serotypes and Salmonella in feedlot runoff, underscoring the need for pretreatment of feedlot runoff before it is disposed into the environment or used as fertilizer.