The molecular epidemiology of plasmid-based dissemination of OXA-48 during a hospital outbreak

Objectives. A large OXA-48 outbreak in the Netherlands involved the spread of OXA-48-producing Enterobacteriaceae among at least 118 patients, suggesting horizontal transfer of this resistance gene through one or more plasmids. Elucidating transmission dynamics of resistance plasmids is hampered by the low resolution of classic typing methods. This study aimed to investigate the molecular epidemiology of plasmids carrying OXA-48 carbapenemase using a next-generation sequencing approach. Methods. A total of 68 OXA-48-producing Enterobacteriaceae isolated from the hospital outbreak, as well as 22 non-outbreak related OXA-48-producing Enterobacteriaceae from the Netherlands, Libya and Turkey were selected. Plasmids were sequenced using the Illumina Miseq platform, and read sets were assembled and analysed. Results. blaOXA-48 was embedded in transposon Tn1999.2 and located on a ca. 62 kb IncL/M conjugative plasmid in 14 different species. There were a maximum of 2 SNPs (single nucleotide polymorphisms) between the core sequence alignment of all plasmids. Closely related sequence variants of this plasmid were detected in non-outbreak isolates from the Netherlands and other countries. Thirty-one of 89 OXA-48-producing isolates also harboured blaCTX-M-15, which was not located on the blaOXA-48-carrying plasmid. Sequencing of four plasmids harbouring blaCTX-M-15 revealed extensive plasmid heterogeneity. Conclusions. A ca. 62 kb plasmid was responsible for the OXA-48 outbreak in a Dutch hospital. Our findings provide strong evidence for both within-host inter-species and between host dissemination of plasmid-based OXA-48 during a nosocomial outbreak. These findings exemplify the complex epidemiology of carbapenemase producing Enterobacteriaceae (CPE).

研究目标：荷兰暴发了一起大规模OXA-48型碳青霉烯酶感染事件，产OXA-48肠杆菌科细菌在至少118名患者中传播，提示该耐药基因可通过一种或多种质粒发生水平转移。经典分型方法分辨率较低，阻碍了耐药质粒传播动力学的阐明。本研究旨在借助下一代测序技术，探究携带OXA-48碳青霉烯酶的质粒的分子流行病学特征。
研究方法：本研究共纳入68株分离自本次医院暴发事件的产OXA-48肠杆菌科细菌，以及22株分别来自荷兰、利比亚和土耳其的非暴发相关产OXA-48肠杆菌科细菌。采用Illumina MiSeq平台对质粒进行测序，并对测序读段进行组装与分析。
研究结果：blaOXA-48嵌入转座子Tn1999.2中，定位于14种不同菌种的约62 kb IncL/M型接合性质粒（IncL/M conjugative plasmid）上。所有质粒的核心序列比对区间内，单核苷酸多态性（single nucleotide polymorphisms, SNPs）最多仅为2个。在来自荷兰及其他国家的非暴发分离株中，亦检测到该质粒的密切相关序列变异体。89株产OXA-48分离株中，有31株同时携带blaCTX-M-15，该基因并未定位于携带blaOXA-48的质粒上。对4株携带blaCTX-M-15的质粒进行测序后发现，其存在广泛的质粒异质性。
研究结论：约62 kb的质粒是荷兰某医院本次OXA-48暴发事件的致病元凶。本研究结果为院内暴发期间，质粒介导的OXA-48在宿主内跨物种传播以及宿主间传播提供了强有力的证据。上述结果亦印证了产碳青霉烯酶肠杆菌科细菌（carbapenemase-producing Enterobacteriaceae, CPE）复杂的流行病学特征。