Molecular epidemiology of a reproductive tract-associated colibacillosis outbreak in a layer breeder flock associated with atypical avian pathogenic Escherichia coli.

The molecular epidemiology of 70 Escherichia coli isolates from an infection outbreak in a layer breeder flock was examined by pulsed-field gel electrophoresis and for a range of virulence factors by polymerase chain reaction. Pulsed-field gel electrophoresis showed 35 of 45 isolates from eight disease cases were associated with a single clonal group that was the exclusive strain associated with reproductive tract. A second unrelated group was found in environmental isolates and healthy birds. The remaining isolates were unrelated to each other or either clonal group. Polymerase chain reaction virulotyping indicated the "epidemic" clonal group contains virulence factors including iss, sfa, tsh, iucC, ibeA, and sitA associated with avian pathogenic E. coli plus several virulence factors more normally associated with human urinary tract infection. Significantly, the "epidemic" clone was also found in an environmental sample, suggesting it may have been transmitted to the flock via the environment.