Proportions and Serogroups of Enterohemorrhagic Shiga Toxin-producing Escherichia coli in Feces of Fed and Cull Beef and Cull Dairy Cattle at Harvest

•The proportion of STEC and EHEC were determined in feces of fed, cull dairy, and cull beef cattle at harvest.•STEC were present in feces of 99.04% of fed cattle, 92.06% of cull dairy, and 91.85% of cull beef cattle.•EHEC were identified in 77.29%, 47.54%, and 38.51%, and confirmed in 7.84%, 5.77%, and 5.01%, of fed, cull dairy, and cull beef cattle feces, respectively.•The most common EHEC confirmed were O157, O26, and O103.•Other EHEC of less common serogroups were isolated, with the most common being O177, O74, O98, and O84. Cattle are considered a primary reservoir of Shiga toxin (stx)-producing Escherichia coli that cause enterohemorrhagic disease (EHEC), and contaminated beef products are one vehicle of transmission to humans. However, animals entering the beef harvest process originate from differing production systems: feedlots, dairies, and beef breeding herds. The objective of this study was to determine if fed cattle, cull dairy, and or cull beef cattle carry differing proportions and serogroups of EHEC at harvest. Feces were collected via rectoanal mucosal swabs (RAMSs) from 1,039 fed cattle, 1,058 cull dairy cattle, and 1,018 cull beef cattle at harvest plants in seven U.S. states (CA, GA, NE, PA, TX, WA, and WI). The proportion of the stx gene in feces of fed cattle (99.04%) was not significantly different (P > 0.05) than in the feces of cull dairy (92.06%) and cull beef (91.85%) cattle. When two additional factors predictive of EHEC (intimin and ecf1 genes) were considered, EHEC was significantly greater (P