Characteristics of plasmid-mediated quinolone resistance genes in extended-spectrum cephalosporin-resistant isolates of Klebsiella pneumoniae and Escherichia coli in Korea.

BACKGROUND

Quinolone resistance is frequently associated with extended-spectrum cephalosporin resistance in Enterobacteriaceae.

METHODS

The characteristics of plasmid-mediated quinolone resistance (PMQR) genes [qnr genes, aac(6')-Ib-cr and qepA] in clinical isolates of Klebsiella pneumoniae and Escherichia coli resistant to extended-spectrum cephalosporin were studied.

RESULTS

5 and 4 of 95 E. coli isolates but 46 (86/187) and 6% (12/187) of K. pneumoniae had qnr and aac(6')-Ib-cr, respectively, and 8 K. pneumoniae contained both genes.qepA was not identified. qnrB, especially qnrB4, was the predominant qnr subtype in K. pneumoniae [94 (88 qnrB of 94 qnr) and 88% (77 qnrB4 of 88 qnrB), respectively], and presence of qnrB4 was closely related with DHA-1 beta-lactamase (99%). However, K. pneumoniae isolates with qnrB4 and bla(DHA-1) were clonally diverse. beta-Lactamases produced by PMQR-containing isolates were variable: CMY-1, CTX-M-14, CTX-M-15, DHA-1, OXA type, SHV-2a, and SHV-12.

CONCLUSION

PMQR genes are widely distributed among clinical isolates of K. pneumoniae, and qnrB4 associated with bla(DHA-1) was the most common PMQR gene in Korea.