Prevalence of the extended-spectrum beta-lactamase and qnr genes in clinical isolates of Escherichia coli.
BACKGROUND
This study was performed to investigate the prevalence of qnr genes in clinical isolates of Escherichia coli from Korea that produce extended-spectrum beta-lactamases (ESBLs).


METHODS
During the period of May to June 2005, we collected clinical isolates of E. coli that were intermediate or resistant to ceftazidime and/or cefotaxime from 11 Korean hospitals. Antimicrobial susceptibility was determined by the disk diffusion and agar dilution methods. ESBL production was confirmed phenotypically by the double-disk synergy test. ESBL and qnr genes were searched for by PCR amplification, and the PCR products were then subjected to direct sequencing.


RESULTS
Double-disk synergy tests were positive in 84.3% (118/140) of ceftazidime- and/or cefotaxime-nonsusceptible E. coli isolates. The most prevalent types of ESBL in E. coli isolates were CTX-M-14 (N=41) and CTX-M-15 (N=58). Other ESBLs were also identified, including CTX-M-3 (N=7), CTX-M-9 (N=8), CTX-M-12 (N=1), CTX-M-57 (N=1), SHV-2a (N=2), SHV-12 (N=17) and TEM-52 (N=4). The qnrA1 and qnrB4 genes were identified in 4 and 7 ESBL-producing isolates, respectively.


CONCLUSIONS
CTX-M-type enzymes were the most common type of ESBL in E. coli isolates from Korea, and the qnr genes were not uncommon in ESBL-producing E. coli isolates. Dissemination of E. coli containing both ESBL and qnr genes could compromise the future usefulness of the expanded-spectrum antibiotics for the treatment of infections.
Park
Yongjung
Y
Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seodaemun-Gu, Seoul, Korea.
Kang
Hyun Kyung
HK
Bae
Il Kwon
IK
Kim
Juwon
J
Kim
Jae Seok
JS
Uh
Young
Y
Jeong
Seok Hoon
SH
Lee
Kyungwon
K
D052978:Disk Diffusion Antimicrobial Tests; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000145:classification / Q000235:genetics*; D006801:Humans; D020128:Inhibitory Concentration 50; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D029968:Escherichia coli Proteins; C485384:Qnr protein, E coli; D001618:beta-Lactamases