The prevalence of plasmid-mediated quinolone resistance determinants among clinical isolates of ESBL or AmpC-producing Escherichia coli from Chinese pediatric patients.

Three kinds of PMQR determinants (qnr genes, aac(6')-Ib-cr, and qepA) have been discovered and shown to be widely distributed among clinical isolates. To characterize the prevalence of PMQR determinants in ESBL or AmpC-producing E. coli clinical isolates in Chinese children, a total of 292 ESBL or AmpC-producing E. coli clinical isolates collected from five children's hospitals in China from 2005 to 2006 were screened for PMQR determinants by PCR. Twenty (6.8%) of the 292 isolates were positive for PMQR determinants. A total of 12 (4.1%) isolates were positive for qnr genes, comprising three positive for qnrA (1.0%), three for qnrB (1.0%), and six for qnrS (2.1%). Twenty-four (8.2%) isolates were positive for aac(6')-Ib, of which 10 (3.4% of 292) had the -cr variant. There was no qepA gene detected in the isolates. Conjugation revealed that qnr, aac(6')-Ib-cr, and ESBL-encoding genes were transferred together.