Molecular Genetic and Functional Analysis of pks-Harboring, Extra-Intestinal Pathogenic Escherichia coli From India

Colibactin, a genotoxin, encoded by the pks pathogenicity island of Escherichia coli belonging to the B2 phylogroup has been increasingly reported as a critical determinant of bacterial pathogenicity. The present study was designed to detect the pks pathogenicity island in extraintestinal pathogenic E. coli (ExPEC) cultured from clinical sources in India. Of 462 pathogenic E. coli analyzed, the pks genomic island was detected in 35 (7.6 %) isolates, which predominantly belonged to pathogenic phylogroup B2 (97%), and harbored virulence genes such as fimH, sfaD/E, and usp. Biofilm formation assay revealed 21 of 35 pks-carrying isolates to be strong (SBF > 1.0), 10 strains to be moderate (SBF = 0.5-1.0), and 4 strains to be weak (SBF < 0.5) biofilm formers. All of the pks-carrying isolates proved resistant against bactericidal activity of human serum and were clonal, as confirmed by PCR based on the Enterobacterial repetitive intergenic consensus (ERIC-PCR). Assays carried out to detect antimicrobial susceptibility revealed 31% of the isolates to be multidrug resistant with 37% carrying ESBL and 25% blaCTX-M-15. The observed prevalence of multidrug resistant and colibactin producing characteristics among pathogenic E. coli belonging to phylogenetic group B2 underscores urgent need for broader surveillance in order to understand and prevent transmission of this extra-intestinal pathogen in community and hospital settings.