Plasmid-mediated quinolone resistance determinants qnr and aac(6')-Ib-cr in extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in China.
OBJECTIVE
To characterize the prevalence of plasmid-mediated quinolone resistance determinants qnr and aac(6')-Ib-cr in extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae.


METHODS
qnrA, qnrB, qnrS, aac(6')-Ib-cr and ESBL-encoding genes were detected by PCR. MICs of 10 antimicrobial agents were determined by Etest. PFGE was used to investigate the clonality of qnr- and aac(6')-Ib-cr-producing isolates. Conjugation and Southern hybridizations were used to confirm whether qnr, aac(6')-Ib-cr or ESBL-encoding genes were located on plasmids.


RESULTS
Twenty-nine (8.0%) of 362 isolates were positive for qnr genes, and the qnrA-, qnrB- and qnrS-type genes were detected alone or in combination in 13 (3.6%), 8 (2.2%) and 9 (2.5%), respectively. Sixty-two (17.1%) isolates were positive for aac(6')-Ib, of which 36 (9.9% of all) had the -cr variant. Conjugation and Southern hybridization revealed that qnrA, aac(6')-Ib-cr and ESBL-encoding genes were always located on the same plasmids.


CONCLUSIONS
qnr and aac(6')-Ib-cr genes were detected in 8.0% and 9.9% of ESBL-producing E. coli and K. pneumoniae, respectively. The plasmids carrying the qnr gene could be transferred by conjugation together with ESBL-encoding genes and aac(6')-Ib-cr.
Jiang
Yan
Y
State Key Laboratory for Diagnosis and Treatment of Infectious Disease, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, China.
Zhou
Zhihui
Z
Qian
Ying
Y
Wei
Zeqing
Z
Yu
Yunsong
Y
Hu
Songnian
S
Li
Lanjuan
L
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D002681:China / Q000453:epidemiology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D005838:Genotype; D006801:Humans; D007710:Klebsiella Infections / Q000453:epidemiology / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*; D015363:Quinolones / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C485384:Qnr protein, E coli; C485385:Qnr protein, Klebsiella pneumoniae; D015363:Quinolones