Nonpathogenic Escherichia coli strains as a surrogate for Shiga toxin–producing E. coli: Fecal shedding dynamics and pen environmental contamination in weaned calves and feedlot steers

Abstract

The purpose of this study was to use nonpathogenic Escherichia coli as a surrogate to assess the transmission dynamics of Shiga toxin–producing E. coli in cattle. Two studies were performed. For the first study, 3 nonpathogenic E. coli strains were orally inoculated into 12 weaned Holsteins calves. Calves were sampled daily the first week and 3 times a week for the following 4 wk. The nonpathogenic E. coli strain with the highest average fecal shedding concentration was chosen for use in the second study. The second study was performed twice over consecutive summers. In each summer, 5 steers were inoculated in a pen of 70 feedlot steers and shedding and transmission were monitored. For the first study, all inoculated strains were shed in the feces of the calves and were detected in the hide, oral, and pen surface samples. During both years of the second study, fecal shedding in the steers was established, as well as transmission of the inoculated strain between steers and into the pen environment. The inoculated strain was also detected in hide surface and oral cavity samples, as well as pen surface, water, and feed samples. These studies provide baseline data on shedding and transmission of a nonpathogenic E. coli strain in dairy calves and feedlot steers and detection in the environment. These data will be useful for studying host-to-host and host-to-environment contact structures and to develop a modeling framework for E. coli transmission in a commercial feedlot setting.