Virulence genes, quinolone and fluoroquinolone resistance, and phylogenetic background of uropathogenic Escherichia coli strains isolated in Japan.

A total of 312 uropathogenic Escherichia coli strains were isolated from clinical specimens in 7 hospitals in Aichi Prefecture, Japan. Among them, 113 strains were resistant to quinolone, and 49 strains were resistant to fluoroquinolone. Phylogenetic group B2 was most prevalent in both susceptible strains (148 of 199 strains, 74.4%) and resistant strains (quinolone-resistant strains, 73 of 113 strains, 64.6%; fluoroquinolone-resistant strains, 40 of 49 strains, 81.6%). The resistant strains showed a significantly lower prevalence of virulence genes papA, hlyA, and cnf1 than did the susceptible strains, and this observation was further obvious when compared within B2 group strains. Among the 40 fluoroquinolone-resistant strains belonging to group B2, 37 (92.5%) strains carried PAIusp subtype IIa, 36 strains of which carried E84V mutation in parC, whereas none of the 9 strains belonging to group D carried PAIusp subtype IIa, and only one strain carried the mutation. These observations indicate that the differences of phenotypes including resistance of quinolone and carriage of virulence genes are associated with the complex context of genetic background, including the phylogenetic group and PAIusp subtype.