Carbapenemase-producing Enterobacteriaceae represent a serious public health threat worldwide. Carbapenemase genes, harbored on a transferable plasmid, have been isolated globally with distinct geographical features. Klebsiella pneumoniae, included in Enterobacteriaceae, also produces carbapenemase and often shows hypervirulence. Overlapping carbapenem resistance and hypervirulence in K. pneumoniae have been reported, but such strains have not yet been found in Japan. Here, we screened 104 carbapenemase-producing K. pneumoniae isolates collected from 37 hospitals and outpatient clinics in Japan between September 2014 and July 2015. PCR and DNA sequencing demonstrated IMP-1 in 21 isolates and IMP-6 in 83 isolates, 77 of which coharbored CTX-M-2. Most of the isolates showed low MICs toward imipenem and meropenem but high MICs toward penicillin and cephalosporins. Conjugation experiments with an Escherichia coli J53 recipient showed that most of the plasmids in IMP-6 producers were transferable, whereas only one-half of the plasmids in IMP-1 producers were transferable. PCR-based replicon typing and multiplex PCR identified five isolates belonging to the CG258 non-tonB79 cluster and no isolate belonging to the CG258-tonB79 cluster or sequence type 307 (ST307). Four K1-ST23 isolates, 10 K2-ST65 isolates, and 7 K2-ST86 isolates were detected that harbored virulence genes. The resistance genes in 85 isolates were transferable, but the virulence genes were not transferred. These results demonstrate the acquisition of IMP-type carbapenemase genes and CTX-M-type genes among hypervirulence isolates in Japan, warranting further attention and countermeasures. In this study, we have determined the molecular characteristics and epidemiology of IMP-6 producers that coharbored various CTX-M genes in Japan.

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日本生产碳青霉烯酶的肺炎克雷伯菌临床分离株的分子和流行病学特征

产生碳青霉烯酶的肠杆菌科细菌在世界范围内代表着严重的公共卫生威胁。带有可转移质粒的碳青霉烯酶基因已在全球范围内分离出来，具有独特的地理特征。肠杆菌科细菌中包含的肺炎克雷伯菌也产生碳青霉烯酶，并经常显示高毒力。已有报道肺炎克雷伯菌中碳青霉烯类药物具有重叠的耐药性和高毒力，但在日本尚未发现这种菌株。在这里，我们筛选了104个产生碳青霉烯酶的肺炎克雷伯菌于2014年9月至2015年7月间从日本37家医院和门诊诊所收集的分离株。PCR和DNA测序显示21个分离株中的IMP-1和83个分离株中的IMP-6，其中7​​7个同伴CTX-M-2。大多数分离株对亚胺培南和美罗培南的MIC较低，而对青霉素和头孢菌素的MIC较高。与大肠杆菌J53受体的缀合实验显示，IMP-6生产者中的大多数质粒是可转移的，而IMP-1生产者中只有一半的质粒是可转移的。基于PCR的复制子分型和多重PCR鉴定了属于CG258 non- tonB79簇的五个分离株，没有属于CG258- tonB79的分离株簇或序列类型307（ST307）。检测到四个带有毒力基因的K1-ST23分离株，10个K2-ST65分离株和7个K2-ST86分离株。85个分离株中的抗性基因是可以转移的，但毒力基因却没有转移。这些结果证明在日本的高毒分离株中获得了IMP型碳青霉烯酶基因和CTX-M型基因，值得进一步关注和采取对策。在这项研究中，我们确定了与日本各种CTX-M基因共存的IMP-6生产者的分子特征和流行病学。