Phylogenetic Groups/B2 Subgroup Distributions, Serogrouping and Identification of Virulence Factors in Extended-Spectrum Cephalosporin-Resistant Escherichia coli Strains Isolated from the Stool of Healthy Children Under 10 Years Old

Background: Segregation of Escherichia coli (E. coli) into the phylogenetic groups was observed in the experiments so that group B2 contained the enteropathogenic E. coli (EPEC) strains and extraintestinal pathogenic E. coli (ExPEC). Objectives: This study aimed to identify B2 phylogenetic groups in the extended-spectrum Cephalosporins resistant E. coli isolated from the stool of healthy children under 10 years old. Methods: One hundred E. coli resistant to broad-spectrum Cephalosporins were collected from the feces of healthy children under 10. Subsequently, we grouped phylogenetic via PCR based on the genes yjaA, chuA, arpA, as well, as TspE4.C2. Then, according to Clermont et al.’s study, we used two individual multiplex PCRs for identifying B2 sub-groups (I-X subgroups). Serogroup typing with the 12 O-antigen was analyzed via PCR, and finally, 10 virulence genes (cnf1, papG, ibeA, malX, usp, cdt, eae, bfp, and afa-Dr) were identified with PCR. Results: The age range of the healthy children was between 1 and 10 years. The B2 and unknown phylogroups were the most common strains in this study. The most common B2 subgroups were I (STc131) (2%), IX (1%), V (8%), IV, V, VII (1%), IX, V (3%), IX, V, III, I (1%), IX, V, III, VII, I (%1), V, I (6%), V, III, I (3%), and V, III, VII (1%), with each subgroup carrying distinctive sets of ExPEC virulence markers. The results also showed that 29% of E. coli in the healthy children had malX and 23% had papGII. It was also found that 32% of the strains isolated from the healthy children had antigens O2 and 36% were unknown. Conclusions: In this study, 27% of the strains belonged to B2 phylogroup and 6% to B1 phylogroup. Moreover, serogroups O2, O16, and O25 were predominant and belonged to B2 phylogroup. Moreover, malX, papGII, usp, papGIII, aggR, and eae virulence genes also had the highest to lowest supply among the tested strains, respectively. Moreover, B2 isolates were shown to have further virulence-related genes in comparison to the non B2 isolates.