Association of Fluoroquinolone Resistance, Virulence Genes, and IncF Plasmids with Extended-Spectrum-β-Lactamase-Producing Escherichia coli Sequence Type 131 (ST131) and ST405 Clonal Groups

The global increase of extended-spectrum-β-lactamase (ESBL)-producingEscherichia coli is associated with the specific clonal group sequence type 131 (ST131). In order to understand the successful spread of ESBL-producingE. coli clonal groups, we characterized fluoroquinolone resistance determinants, virulence genotypes, and plasmid replicons of ST131 and another global clonal group, ST405. We investigated 41 ST131-O25b, 26 ST131-O16, 41 ST405, and 41 other ST (OST) ESBL-producing isolates, which were collected at seven acute care hospitals in Japan. The detection of ESBL types, fluoroquinolone resistance-associated mutations (including quinolone resistance-determining regions [QRDRs]), virulence genotypes, plasmid replicon types, and IncF replicon sequence types was performed using PCR and sequencing.bla CTX-M , specificallybla CTX-M-14 , was the most common ESBL gene type among the four groups. Ciprofloxacin resistance was found in 90% of ST131-O25b, 19% of ST131-O16, 100% of ST405, and 54% of OST isolates. Multidrug resistance was more common in the ST405 group than in the ST131-O25 group (56% versus 32%;P = 0.045). All ST131-O25b isolates except one had four characteristic mutations in QRDRs, but most of the isolates from the other three groups had three mutations in common. The ST131-O25b and ST405 groups had larger numbers of virulence genes than the OST group. All of the ST131-O25b and ST405 isolates and most of the ST131-O16 and OST isolates carried IncF replicons. The most prevalent IncF replicon sequence types differed between the four clonal groups. Both the ST131-O25b and ST405 clonal groups had a fluoroquinolone resistance mechanism in QRDRs, multidrug resistance, high virulence, and IncF plasmids, suggesting the potential for further global expansion and a need for measures against these clonal groups.