Plasmid-mediated quinolone resistance determinants in Enterobacteriaceae from urine clinical samples

Abstract

Plasmid-mediated quinolone resistance (PMQR) determinants including, qnrA, qnrB, qnrC, qnrD, qnrS, aac(6′)-Ib-cr, oqxAB, and qepA, were investigated in 214 Enterobacteriaceae strains from urine clinical samples. Antimicrobial susceptibility testing for ciprofloxacin, ceftriaxone, and imipenem was performed by broth microdilution method. All strains were screened for PMQR genes by PCR. Virulence determinants, namely afa, pap, pil, sfa/foc, and kpsMT of eight Escherichia coli strains proven positive for at least one qnr gene, were investigated by PCR. All of the eight investigated strains carried the pil gene, showing that P fimbria is a common virulence determinant among qnr positive E. coli. Out of 214 tested strains, 38 yielded any PMQR determinant, altogether 45 genes were detected namely, 6 qnrA, 1 qnrB, 2 qnrD and 8 qnrS, 9 aac(6′)-Ib-cr, and 19 oqxAB; however, neither qepA nor qnrC were detected. Notably, 18 Klebsiella spp., harbored oqxAB, nine E. coli were positive for qnrS and two Morganella morganii yielded qnrD resistance determinant. In this study, we demonstrated 17.7% prevalence of PMQR-positive Enterobacteriaceae and first reported qnrD-resistance determinant in Hungary. Altogether, 25 PMQR-positive strains were susceptible or low-level resistant to ciprofloxacin with minimum inhibitory concentration (MIC) between 0.06 and 1 mg/L, suggesting that prevalence of PMQR determinants is underestimated and screening among clinical isolates exhibiting reduced susceptibility is necessary. Fluoroquinolone resistance breakpoints of Enterobacteriaceae were revised in 2017 by European Committee of Antimicrobial Susceptibility Testing indicating ciprofloxacin susceptibility only until 0.25 mg/L MIC value.