Genetic diversity, phylogroup distribution and virulence gene profile of pks positive Escherichia coli colonizing human intestinal polyps

Some Escherichia coli strains of phylogroup B2 harbor a (pks) pathogenicity island that encodes a polyketide-peptide genotoxin called colibactin. It causes DNA double-strand breaks and megalocytosis in eukaryotic cellsand it may contribute to cancer development. Study of bacterial community that colonizes the adenomatouspolyp lesion, defined as precancerous lesions, could be helpful to assess if such pathogenic bacteria possess a rolein the polyp progression to cancer. In this cross-sectional study, a total of 1500 E. coli isolates were obtained frombiopsies of patients presenting adenomatous colon polyps, the normal tissues adjacent to the polyp lesion andpatients presenting normal mucosa. pks island frequency, phylogenetic grouping, fingerprint genotyping, andvirulence gene features of pks positive (pks+) E. coli isolates were performed. We found pks+E. coli stronglycolonize two patients presenting polypoid lesions and none were identified in patients presenting normal mu-cosa. Predominant phylogroups among pks+E. coli isolates were B2, followed by D. Clustering based on frag-ment profiles of composite analysis, typed the pks+isolates into 5 major clusters (I–V) and 17 sub-clusters,demonstrating a high level of genetic diversity among them. The most prevalent virulence genes were fimH andfyuA (100%), followed by vat (92%), hra and papA (69%), ibeA (28%), and hlyA (25%). Our results revealed thatpks+E. coli can colonize the precancerous lesions, with a high distribution in both the polyp lesions and innormal tissues adjacent to the lesion. The high differences in fingerprinting patterns obtained indicate that pks+E. coli strains were genetically diverse, possibly allowing them to more easily adapt to environmental variations.