The distribution and genetic structure of Escherichia coli in Australian vertebrates: host and geographic effects

Abstract

Escherichia coliwas isolated from more than 2300 non-domesticated vertebrate hosts living in Australia.E. coliwas most prevalent in mammals, less prevalent in birds and uncommon in fish, frogs and reptiles. Mammals were unlikely to harbourE. coliif they lived in regions with a desert climate and less likely to haveE. coliif they lived in the tropics than if they lived in semi-arid or temperate regions. In mammals, the likelihood of isolatingE. colifrom an individual depended on the diet of the host andE. coliwas less prevalent in carnivores than in herbivores or omnivores. In both birds and mammals, the probability of isolatingE. coliincreased with the body mass of the host. Hosts living in close proximity to human habitation were more likely to harbourE. colithan hosts living away from people. The relative abundance ofE. coligroups A, B1, B2 and D strains in mammals depended on climate, host diet and body mass. Group A strains were uncommon, but were isolated from both ectothermic and endothermic vertebrates. Group B1 strains could also be isolated from any vertebrate group, but were predominant in ectothermic vertebrates, birds and carnivorous mammals. Group B2 strains were unlikely to be isolated from ectotherms and were most abundant in omnivorous and herbivorous mammals. Group D strains were rare in ectotherms and uncommon in endotherms, but were equally abundant in birds and mammals. The results of this study suggest that, at the species level, the ecological niche ofE. coliis mammals with hindgut modifications to enable microbial fermentation, or in the absence of a modified hindgut,E. colican only establish a population in ‘large-bodied’ hosts. The non-random distribution ofE. coligenotypes among the different host groups indicates that strains of the fourE. coligroups may differ in their ecological niches and life-history characteristics.