Fecal Colonization of Enterobacteriaceae Carrying Plasmid-Mediated Quinolone Resistance Determinants in Korea

Abstract

The aims of the current study were to investigate the prevalence and molecular characteristics of plasmidmediated quinolone resistance (PMQR) genes from colonizing fecal organisms and to compare the incidence and subtype of these genes according to bacterial species and hospital at five tertiary-care hospitals in Korea. A total of 500 nonduplicated clinical isolates of Enterobacteriaceae were obtained from fecal specimens at five tertiary-care hospitals between March and May 2008. The PMQR genes (qnrA, qnrB, qnrS, aac(6’)-Ib-cr, and qepA) were amplified by PCR and confirmed by direct sequencing of the PCR products. A total of 83 (16.6%) qnr-positive isolates were detected. The prevalence rates of qnrA, qnrB, and qnrS were 1.4%, 13.6%, and 1.6%, respectively. The species distributions of qnrB-positive isolates were Klebsiella pneumoniae (37/109; 33.9%), Citrobacter freundii (10/34; 29.4%), Citrobacter braakii (8/13; 61.5%), and Escherichia coli (8/275; 2.9%). Sixteen subtypes of qnrB were detected, including seven novel variants. The prevalences of aac(6’)-Ib-cr and qepA were 15.6% (n = 78) and 0.6% (n = 3), respectively. The aac(6’)-Ib-cr gene was detected in 39 (47.0%) of 83 qnr-positive isolates and 39 (9.4%) of 417 qnr-negative isolates There was one qepA variant containing a novel mutation (Ala231Val). The prevalence of PMQR genes was high in Enterobacteriaceae from stool specimens in Korea, and there was a close relation between qnr and aac(6’)-Ib-cr.