Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates are known to tolerate superior quinolone antimicrobials compared with other antibacterial agents. Among the clones belonging to sequence type (ST) 131 by multilocus sequence typing, the involvement of the H30-Rx subclone has been reported worldwide with various fimH genes encoding type 1 pili. We investigated 83 isolates of ESBL-producing E. coli and performed antimicrobial susceptibility test, CH (fumC/fimH) ST131 by typing the specific PCR. Moreover, mutation analysis of genes involved in quinolone antibiotic resistance (gyrA and parC) and ESBL genotypes were determined. As a result, 54 of 83 isolates (65.1%) of CH40-30 clones corresponding to ST131-fimH30 were detected, and all were resistant to levofloxacin. Mutations associated with this resistance were common, and included S83L and D87N of gyrA and S80I and E84V of parC. Subclone analysis revealed a high proportion of fimH30-non-Rx (40 isolates, 74.1%). Each subclone was characterized by ESBL genotype, and the CTX-M-15 type was mainly seen for fimH30-Rx, with the CTX-M-14 type or CTX-M-27 type seen for fimH30-non-Rx. This study suggests that an increase in ESBL-producing quinolone-resistant E. coli in a city hospital in Hyogo, Japan, was caused by the spread of subclones belonging to fimH30-non-Rx of ST131.
Keywords: CH typing; ESBL; Escherichia coli; ST131; fimH.