Comparative genotypic and phenotypic characteristics of human associated extraintestinal Escherichia coli isolated from cats and dogs




Bourne, Judith

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Escherichia coli extraintestinal infections (ExPEC) cause significant disease in humans and companion animals (cats and dogs) predominantly urinary tract infections, but also sepsis and neonatal meningitis. E. coli also causes avian pathogenic E. coli (APEC), a very important cause of mortality and morbidity in poultry. E. coli inhabiting the hindgut of healthy humans, companion animals and chickens is regarded as a potential source of ExPEC and APEC strains. The common, close relationship of cats and dogs with people and their frequent exposure to chicken meat has raised concerns that companion animals and chicken meat may serve as reservoirs for ExPEC in humans, as well as a source of antibiotic resistant strains. This study showed that the most important human ExPEC sequence types (ST) (ST69, ST73, ST95 and ST131) within phylogroups B2 and D, could be isolated from faeces collected from healthy domestic cats and dogs in Canberra. This was especially the case for cats and ST73. This ST was isolated from a greater proportion of cat faecal samples than faecal and clinical samples from humans. Genotypic analysis of these isolates and comparison with genomes of strains isolated from people and poultry meat showed that within each sequence type there were discrete host related clusters. In depth analysis of the cat and human ST73 strains indicated sharing between hosts had occurred. Some differences in gene carriage by strains and phenotypic differences could be explained as host adaptations. The findings from this study support the hypothesis that transmission of ExPEC strains occurs between humans, chicken meat and cats, but also provides evidence of host specificity. Thus, further study of isolate attributes which contribute to zoonotic potential and host adaptation must go beyond studying isolates at the phylogroup or sequence type level and examine WGS subgroups to understand the relatedness of E. coli isolated from different hosts.






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