Department of Medical Microbiology, University Medical Centre Utrecht, Utrecht, The Netherlands.
PLoS One. 2012;7(12):e52102. doi: 10.1371/journal.pone.0052102. Epub 2012 Dec 20.
There is a global increase in infections caused by Enterobacteriaceae with plasmid-borne β-lactamases that confer resistance to third-generation cephalosporins. The epidemiology of these bacteria is not well understood, and was, therefore, investigated in a selection of 636 clinical Enterobacteriaceae with a minimal inhibitory concentration >1 mg/L for ceftazidime/ceftriaxone from a national survey (75% E. coli, 11% E. cloacae, 11% K. pneumoniae, 2% K. oxytoca, 2% P. mirabilis). Isolates were investigated for extended-spectrum β-lactamases (ESBLs) and ampC genes using microarray, PCR, gene sequencing and molecular straintyping (Diversilab and multi-locus sequence typing (MLST)). ESBL genes were demonstrated in 512 isolates (81%); of which 446 (87%) belonged to the CTX-M family. Among 314 randomly selected and sequenced isolates, bla(CTX-M-15) was most prevalent (n = 124, 39%), followed by bla(CTX-M-1) (n = 47, 15%), bla(CTX-M-14) (n = 15, 5%), bla(SHV-12) (n = 24, 8%) and bla(TEM-52) (n = 13, 4%). Among 181 isolates with MIC ≥16 mg/L for cefoxitin plasmid encoded AmpCs were detected in 32 and 27 were of the CMY-2 group. Among 102 E. coli isolates with MIC ≥16 mg/L for cefoxitin ampC promoter mutations were identified in 29 (28%). Based on Diversilab genotyping of 608 isolates (similarity cut-off >98%) discriminatory indices of bacteria with ESBL and/or ampC genes were 0.994, 0.985 and 0.994 for E. coli, K. pneumoniae and E. cloacae, respectively. Based on similarity cut-off >95% two large clusters of E. coli were apparent (of 43 and 30 isolates) and 21 of 21 that were typed by belonged to ST131 of which 13 contained bla(CTX-M-15). Our findings demonstrate that bla(CTX-M-15) is the most prevalent ESBL and we report a larger than previously reported prevalence of ampC genes among Enterobacteriaceae responsible for resistance to third-generation cephalosporins.
全球范围内，由质粒携带的β-内酰胺酶引起的对第三代头孢菌素具有耐药性的肠杆菌科感染正在增加。这些细菌的流行病学情况尚未得到充分了解，因此在一项全国性调查中对最小抑菌浓度（MIC）＞1mg/L 的头孢他啶/头孢曲松的 636 株临床肠杆菌科（75%大肠埃希菌、11%阴沟肠杆菌、11%肺炎克雷伯菌、2%产酸克雷伯菌、2%奇异变形杆菌）进行了研究。使用微阵列、PCR、基因测序和分子菌株分型（Diversilab 和多位点序列分型（MLST））对这些分离株进行了超广谱β-内酰胺酶（ESBLs）和ampC 基因的检测。在 512 株分离株（81%）中证实存在 ESBL 基因，其中 446 株（87%）属于 CTX-M 家族。在随机选择的 314 株测序分离株中，bla（CTX-M-15）最为常见（n=124，39%），其次是 bla（CTX-M-1）（n=47，15%）、bla（CTX-M-14）（n=15，5%）、bla（SHV-12）（n=24，8%）和 bla（TEM-52）（n=13，4%）。在 181 株对头孢西丁 MIC≥16mg/L 的分离株中，有 32 株携带质粒编码的 AmpC，其中 27 株为 CMY-2 组。在 102 株对头孢西丁 MIC≥16mg/L 的大肠埃希菌分离株中，有 29 株（28%）发现 ampC 启动子突变。基于 608 株分离株的 Diversilab 基因分型（相似性截断值＞98%），大肠埃希菌、肺炎克雷伯菌和阴沟肠杆菌中具有 ESBL 和/或 ampC 基因的细菌的鉴别指数分别为 0.994、0.985 和 0.994。基于相似性截断值＞95%，可明显分为两个大的大肠埃希菌群（43 株和 30 株），其中 21 株均属于 ST131，其中 13 株含有 bla（CTX-M-15）。我们的研究结果表明，bla（CTX-M-15）是最常见的 ESBL，并且我们报告了对第三代头孢菌素耐药的肠杆菌科中 ampC 基因的流行率高于以往报道。
