Impact of vaccination on the ecology of Escherichia coli in commercial Turkey production

Escherichia coli is a bacterium ubiquitous to the healthy intestinal microflora in animals. Some E. coli can cause disease in poultry, but disease manifestation is a result of the balance between stress level in the bird and the virulence potential of E. coli strains present. The collection of diseases caused by E. coli is referred to as colibacillosis, which has continually burdened the poultry industry through significant morbidity, mortality, condemnations, and reduced performance. Avian pathogenic E. coli (APEC) refers to strains with shared genetic traits enhancing their ability to cause colibacillosis and have been well characterized. However, less is known about the overall ecology of E. coli in poultry production and how ecology changes following mitigation strategies such as vaccination. We examined commensal and environmental E. coli isolates from samples collected as part of a field trial consisting of 8 flocks (4 control and 4 vaccinated) located within a single, vertically integrated, turkey production company. Our results revealed no significant differences in APEC status or proportions of high-risk clones in response to vaccination. APEC prevalence was significantly higher during the growout versus brood period. When we looked at Clermont phylogroups, no significant differences were seen in the prevalence of phylogroups B1, C, D, E, F, and G between the control and vaccinated groups. Phylogroup B2 prevalence was significantly higher while phylogroup A prevalence was significantly lower in the vaccinated group compared to the control group during the growout period, but only for isolates from cloacal swabs. Phylogroups A, B1, B2, C, and E showed differences in prevalence between the brood and growout periods, but no relationships were consistently significant across all sample types. These findings suggest that application of a live attenuated vaccine has limited effects on the overall ecology of E. coli and APEC prevalence within healthy birds.