Temporal Shedding Patterns and Virulence Factors ofEscherichia coliSerogroups O26, O103, O111, O145, and O157 in a Cohort of Beef Calves and Their Dams

Abstract

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 vtx 1 , eae, and ehl genes, 6.5% carried vtx 1 and vtx 2 , and one isolate carried vtx 2 only. Serogroup O26 isolates comprised seven pulsed-field gel electrophoresis (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 vtx 2 , and none carried vtx 1 . Serogroup O103 isolates comprised 10 PFGE patterns and were dominated by two patterns representing 62.5% of isolates. Shedding of E. coli O145 and O157 was rare. All serogroup O145 isolates carried eae, but none carried vtx 1 or vtx 2 . All but one serogroup O157 isolate carried vtx 2 , 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 three times as many samples as E. coli O103, and the rate at which calves began shedding E. coli O26 for the first time was five times greater than that for E. coli O103. For E. coli O26, O103, and O157, there was no association between shedding by calves and shedding by dams within 1 week of birth. For E. coli O26 and O103, there was no association between shedding and scouring, and there was no significant change in shedding following housing.

Molecular Epidemiology of Antimicrobial-Resistant Commensal Escherichia coli Strains in a Cohort of Newborn Calves

“…The presence of such a transferable element carried by one of the genotypes within this cohort has implications for the possible transmission of resistance to cohabiting pathogens. Verotoxigenic E. coli strains were also identified within this cohort over the same period (35), and studies to examine whether these pathogens will accept resis-tance plasmids isolated from the commensal population are ongoing. Transmission of multiple-resistance phenotypes between epidemiologically unrelated commensal and pathogenic E. coli strains has recently been demonstrated in vitro under ileal conditions (7).…”

Modelling the epidemiology of Verocytotoxin-producing Escherichia coli serogroups in young calves

“…For the method to detect a particular VTEC serogroup, the number of organisms in each faecal sample must be above a detection threshold [10,14]. Furthermore, Pearce et al [15] used immunomagnetic separation (IMS) to detect VTEC in the same calf cohort and detected serogroup O145, which was not isolated by the PCR/DNA probe hybridization method used by Shaw et al [10]. Therefore, it is possible that the number of serogroups observed per sample (or even across the whole calf cohort) might be limited by the detection method used.…”

Distribution of tccP in Clinical Enterohemorrhagic and Enteropathogenic Escherichia coli Isolates

“…EHEC can be isolated directly from the feces of large farm animals, in particular, calves and adult cattle, which represent an important source of human infection (24). Humans can become infected with EHEC through the consumption of contaminated food or by direct transmission from infected animals or humans.…”