Phylogenetic typing
The E. coli isolates can be classified into eight phylo-groups: seven (A, B1, B2, C, D, E, and F). Unlike isolates were assigned to the corresponding groups based on four genetic markers, namely arpA ,yjaA , chuA , and TspE4.C2 . The phylogenetic grouping of the E. coli isolates was carried out by using a quadruplex PCR reaction (Clermont et al., 2013). All the primer sequences and PCR conditions are given in Table S1.