Park Yeon-Joon, Yu Jin Kyung, Lee Seungok, Oh Eun-Jee, Woo Gun-Jo
Department of Clinical Pathology, College of Medicine, The Catholic University of Korea, Kangnam St Mary's Hospital, 505 Banpo-dong, Seocho-ku, Seoul 137-701, Korea.
J Antimicrob Chemother. 2007 Oct;60(4):868-71. doi: 10.1093/jac/dkm266. Epub 2007 Jul 27.
To investigate the prevalence of qnr determinants, their influence on quinolone susceptibility and their association with other plasmid-mediated genes in AmpC-producing Enterobacteriaceae without any selection criteria.
A total of 644 consecutive, non-duplicate isolates of Enterobacter cloacae (186), Enterobacter aerogenes (154), Citrobacter freundii (138) and Serratia marcescens (166) were examined. We performed antimicrobial susceptibility testing and PCR for qnr determinants (qnrA, qnrB and qnrS), extended-spectrum beta-lactamase (ESBL) (bla(TEM), bla(SHV) and bla(CTX-M)), orf513, orf1005 and bla(DHA-1.) To differentiate qnr subtypes, restriction enzyme analysis and sequencing was performed.
The prevalence of qnr determinants was high in C. freundii (38.4%) and E. cloacae (28.5%), but low in E. aerogenes (3.2%) and S. marcescens (2.4%). qnrA1 was most frequent in E. cloacae, and qnrB was prevalent in C. freundii. All the qnrA- and qnrB4-positive isolates showed ciprofloxacin MICs > or = 0.5 mg/L and nalidixic acid MICs > or = 16 mg/L. However, the B1 and B2 subtypes showed a wide range of quinolone MICs. In relation to ESBLs, we found that qnrA1, qnrB2 and qnrB4 producers were significantly more frequent among ESBL producers (P < 0.05). Twelve of 13 qnrB4 producers harboured bla(DHA-1). orf513 was detected in 43 isolates of the 47 isolates with co-resident qnr and ESBL genes. None of the qnr producers harboured orf1005.
The prevalence of qnrA and qnrB was high among C. freundii and E. cloacae in Korea and there were characteristics unique to the qnr subtypes. Quinolones should be used cautiously in these species, especially when they are ESBL producers.
在无任何选择标准的产AmpC酶肠杆菌科细菌中，调查qnr决定簇的流行情况、其对喹诺酮敏感性的影响及其与其他质粒介导基因的关联。
共检测了644株连续的、非重复的阴沟肠杆菌（186株）、产气肠杆菌（154株）、弗氏柠檬酸杆菌（138株）和粘质沙雷氏菌（166株）。我们进行了抗菌药物敏感性试验以及针对qnr决定簇（qnrA、qnrB和qnrS）、超广谱β-内酰胺酶（ESBL）（bla(TEM)、bla(SHV)和bla(CTX-M)）、orf513、orf1005和bla(DHA-1)的PCR检测。为区分qnr亚型，进行了限制性内切酶分析和测序。
qnr决定簇在弗氏柠檬酸杆菌（38.4%）和阴沟肠杆菌（28.5%）中的流行率较高，而在产气肠杆菌（3.2%）和粘质沙雷氏菌（2.4%）中较低。qnrA1在阴沟肠杆菌中最为常见，qnrB在弗氏柠檬酸杆菌中普遍存在。所有qnrA和qnrB4阳性菌株的环丙沙星MIC≥0.5 mg/L，萘啶酸MIC≥16 mg/L。然而，B1和B2亚型显示出广泛的喹诺酮MIC范围。关于ESBL，我们发现qnrA1、qnrB2和qnrB4产生菌在ESBL产生菌中明显更为常见（P<0.05）。13株qnrB4产生菌中有12株携带bla(DHA-1)。在47株同时携带qnr和ESBL基因的菌株中，有43株检测到orf513。没有qnr产生菌携带orf1005。
在韩国的弗氏柠檬酸杆菌和阴沟肠杆菌中，qnrA和qnrB的流行率较高，且qnr亚型具有独特特征。在这些菌种中应谨慎使用喹诺酮类药物，尤其是当它们是ESBL产生菌时。
