Background: The widespread Escherichia coli clone ST131 implicated in multidrug-resistant infections has been\nrecently reported, the majority belonging to O25:H4 serotype and classified into five main virotypes in accordance\nwith the virulence genes carried.\nMethods: Pathogenicity Islands I and II (PAI-I and PAI-II) were determined using conventional PCR protocols from a\nset of four E. coli CTXR ST131 O25:H4/H30-Rx strains collected from healthy donorsâ?? stool. The virulence genes patterns\nwere also analyzed and compared them with the virotypes reported previously; then adherence, invasion,\nmacrophage survival and biofilm formation assays were evaluated and AIEC pathotype genetic determinants were\ninvestigated.\nFindings: Non-reported virulence patterns were found in our isolates, two of them carried satA, papA, papGII genes\nand the two-remaining isolates carried cnfI, iroN, satA, papA, papGII genes, and none of them belonged to classical\nST131 virotypes, suggesting an endemic distribution of virulence genes and two new virotypes. The presence of PAI-I\nand PAI-II of Uropathogenic E. coli was determined in three of the four strains, furthermore adherence and invasion\nassays demonstrated higher degrees of attachment/invasion compared with the control strains. We also amplified\nintI1, insA and insB genes in all four samples.\nInterpretation: The results indicate that these strains own non-reported virotypes suggesting endemic distribution\nof virulence genes, our four strains also belong to an AIEC pathotype, being this the first report of AIEC in Mexico and\nthe association of AIEC with healthy donors.
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