High prevalence of plasmid-mediated quinolone resistance genes qnr and aac(6')-Ib-cr in clinical isolates of Enterobacteriaceae from nine teaching hospitals in China.
Quinolone resistance is an emerging problem in China. To investigate the prevalence of the plasmid-mediated quinolone resistance genes qnr and aac(6')-Ib-cr, a total of 265 clinical isolates of Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, and Enterobacter cloacae with ciprofloxacin MICs of > or =0.25 microg/ml were screened at nine teaching hospitals in China. The qnrA, qnrB, qnrS, and aac(6')-Ib genes were detected by PCR. The aac(6')-Ib-cr gene was further identified by digestion with BtsCI and/or direct sequencing. The qnr gene was present in significantly smaller numbers of isolates with cefotaxime MICs of <2 microg/ml than isolates with higher MICs (> or =2.0 microg/ml) (20.6% and 42.1%, respectively; P < 0.05). aac(6')-Ib-cr was present in 17.0% of the isolates tested, and 7.9% of the isolates carried both the qnr and the aac(6')-Ib-cr genes. Among the isolates with cefotaxime MICs of > or =2.0 microg/ml, qnr and aac(6')-Ib-cr were present in 65.7% and 8.6% of E. cloacae isolates, respectively; 65.5% and 21.8% of K. pneumoniae isolates, respectively; 63.3% and 26.7% of C. freundii isolates, respectively; and 6.5% and 16.9% of E. coli isolates, respectively. The 20 transconjugants showed 16- to 128-fold increases in ciprofloxacin MICs, 14 showed 16- to 2,000-fold increases in cefotaxime MICs, and 5 showed 8- to 32-fold increases in cefoxitin MICs relative to those of the recipient due to the cotransmission of bla(CTX-M-14), bla(CTX-M-3), bla(DHA-1), bla(SHV-2), and bla(SHV-12) with the qnr and aac(6')-Ib-cr genes. Southern hybridization analysis showed that these genes were located on large plasmids of different sizes (53 to 193 kb). These findings indicate the high prevalence of qnr and aac(6')-Ib-cr in members of the family Enterobacteriaceae and the widespread dissemination of multidrug resistance in China.
Yang
Hong
H
Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, No. 1 Shuaifuyuan, Wangfujing, Beijing 100730, China.
Chen
Hongbin
H
Yang
Qiwen
Q
Chen
Minjun
M
Wang
Hui
H
D000123:Acetyltransferases / Q000235:genetics; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002681:China / Q000453:epidemiology; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000453:epidemiology* / Q000382:microbiology; D006784:Hospitals, Teaching; D006801:Humans; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015995:Prevalence; D015363:Quinolones / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015363:Quinolones; D000123:Acetyltransferases; C019681:aminoglycoside acetyltransferase