Phylogenetic group determination of faecal Escherichia coli and comparative analysis among different hosts

Phylogenetic analysis has shown that Escherichia coli is composed of four main phylogenetic groups (A, B1, B2 and D). Characterization of phylogenetic groups is of clinical interest, as group A and B1 generally associated with commensals, whereas most enteropathogenic isolates are assigned to group D, and group B2 is associated with extra-intestinal pathotype. One hundred E. coli strains recovered from faecal samples of dog, chicken, ruminants (sheep, goat and cattle) and human were subjected to phylogenetic analysis based on triplex PCR method, according to a combination of three genetic markers chuA, yjaA and DNAfragment TspE4.C2. The majority of collected isolates belonged to group D (44%), followed by groups A (32%), and B2 (24%). By sample origin, groups D, A, and B2 were prevalent in 16.7, 50, and 33.3%, respectively for dog isolates; 52.8, 36.1, and 11.1% for chicken isolates; 41.2, 29.4, and 29.4% for ruminants isolates; and 60.9, 8.7, and 30.4% for human isolates, respectively and none of the strains among all the analysed hosts belong to group B1. This study suggests there was a significant difference in the E. coli phylogenetic groups, subgroups and genetic markers among the different hosts analysed.