Temporal Shedding Patterns and Virulence Factors of Escherichia coli

This study investigated the shedding of Escherichia coli O26, O103, O111, O145, and O157 in a cohort of beef calves from birth over a 5-month period and assessed the relationship between shedding in calves and shedding in their dams, the relationship between shedding and scouring in calves, and the effect of housing on shedding in calves. Fecal samples were tested by immunomagnetic separation and by PCR and DNA hybridization assays. E. coli O26 was shed by 94 % of calves. Over 90 % of E. coli O26 isolates carried the vtx1, eae, and ehl genes, 6.5 % carried vtx1 and vtx2, and one isolate carried vtx2 only. Serogroup O26 isolates comprised seven pulsed-field gel electro-phoresis (PFGE) patterns but were dominated by one pattern which represented 85.7 % of isolates. E. coli O103 was shed by 51 % of calves. Forty-eight percent of E. coli O103 isolates carried eae and ehl, 2 % carried vtx2, and none carried vtx1. Serogroup O103 isolates comprised 10 PFGE patterns and were dominated by two patterns represent-ing 62.5 % of isolates. Shedding of E. coli O145 and O157 was rare. All serogroup O145 isolates carried eae, but none carried vtx1 or vtx2. All but one serogroup O157 isolate carried vtx2, eae, and ehl. E. coli O111 was not detected. In most calves, the temporal pattern of E. coli O26 and O103 shedding was random. E. coli O26 was detected in thre