Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.
J Antimicrob Chemother. 2011 Oct;66(10):2255-62. doi: 10.1093/jac/dkr283. Epub 2011 Jul 6.
Extended-spectrum β-lactamases (ESBLs) have become a problem among AmpC-producing Enterobacteriaceae and the emergence of concomitant quinolone resistance in β-lactamase-producing isolates poses a global threat. In this study we investigated the prevalence and regional variation of ESBLs in Japanese clinical isolates of Citrobacter spp. and analysed plasmid-mediated quinolone resistance (PMQR) determinants in ESBL-producing Citrobacter spp.
A total of 348 clinical isolates of Citrobacter spp. collected throughout Japan were studied. Screening and the boronic acid disc test were performed to detect ESBLs in Citrobacter spp. with chromosomal AmpC β-lactamases. PCR and sequencing were done to identify ESBL and PMQR genes. For ESBL-producing Citrobacter spp., PFGE was performed using the SfiI restriction enzyme.
The number of ESBL-producing isolates confirmed phenotypically was 67 (19.3%). The prevalence of ESBL-producing Citrobacter koseri was significantly higher (32.1%) than that of ESBL-producing Citrobacter freundii (4.6%) (P < 0.01). Moreover, the prevalence of ESBLs was notably higher among C. koseri from southern Japan (60.0%). CTX-M-2 was predominant in C. koseri. Of the ESBL-producing C. koseri analysed, 23.2% possessed PMQR determinants, and there was a significant association between qnrB4 and bla(SHV-12). The 57 ESBL-producing Citrobacter spp. possessing bla(CTX-M), bla(SHV) or bla(TEM) were divided into 18 unique PFGE types.
This is the first report about the prevalence of PMQR determinants among ESBL-producing Citrobacter spp. from Japan. Our data suggest that ESBLs and PMQR determinants are spreading among C. koseri in Japan.
产 AmpC 型肠杆菌科细菌中的超广谱β-内酰胺酶（ESBLs）已成为一个问题，同时产β-内酰胺酶分离株中出现的协同性喹诺酮耐药性对全球构成威胁。在这项研究中，我们调查了日本产柠檬酸杆菌临床分离株中 ESBL 的流行情况和地区差异，并分析了产 ESBL 型柠檬酸杆菌中的质粒介导的喹诺酮耐药（PMQR）决定因素。
研究共纳入了日本各地收集的 348 株柠檬酸杆菌临床分离株。采用筛选和硼酸盘试验检测产柠檬酸杆菌中染色体 AmpC 型β-内酰胺酶的 ESBL。通过 PCR 和测序鉴定 ESBL 和 PMQR 基因。对于产 ESBL 的柠檬酸杆菌，采用 SfiI 限制性内切酶进行 PFGE。
通过表型确证的产 ESBL 分离株数量为 67 株（19.3%）。产 ESBL 型柠檬酸格氏肠杆菌的流行率明显高于产 ESBL 型柠檬酸弗氏肠杆菌（32.1%比 4.6%）（P＜0.01）。此外，来自日本南部的 C. koseri 中 ESBL 的流行率明显更高（60.0%）。CTX-M-2 在 C. koseri 中占优势。在分析的产 ESBL 型 C. koseri 中，23.2%具有 PMQR 决定因素，qnrB4 与 bla(SHV-12) 之间存在显著关联。携带 bla(CTX-M)、bla(SHV)或 bla(TEM)的 57 株产 ESBL 型柠檬酸杆菌分为 18 种独特的 PFGE 型。
这是日本首次报道产 ESBL 型柠檬酸杆菌中 PMQR 决定因素的流行情况。我们的数据表明，ESBLs 和 PMQR 决定因素正在日本的 C. koseri 中传播。
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