Molecular epidemiology of carbapenem-resistant hypervirulent Klebsiella pneumoniae in China

The epidemiological features of the newly emerged carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-HvKP) and its potential threat to human health are currently unknown. In this study, a total of 784 blaKPC-2-bearing CRKP strains collected from three hospitals located at different geographical locales in China during 2014–2017 were subjected to molecular typing, screening of virulence plasmid, string test and WGS (367/784 strains). The proportion of CRKP among all clinical K. pneumoniae strains increased sharply in China during 2014–2017. A large proportion (58%) of these CRKP strains were found to harbour a virulence-encoding plasmid, while only 13% of such strains exhibited a hypervirulent phenotype by string test and neutrophil assay. The lack of hypervirulent phenotype in virulent plasmid-bearing CRKP strains was found to be due to the mutation’s presence on rmpA and rmpA2 genes, which rendered them non-functional, while some strains carrying wild type rmpA did not exhibit hypervirulent phenotype either suggesting that other factors might also contribute to the hypervirulence of CRKP. Phylogenetic and SNP analysis indicated that the transmission of these CRKP strains in China likely involved several major clones of ST11. Carriage of IncFII pSWU01-like, blaKPC-2-bearing plasmid was found to be the major mechanism of carbapenem resistance in these CRKP strains. In conclusion, our data indicated that the prevalence of CRKP strains carrying the virulence plasmid has rapidly increased in China, while genetic markers were not correlated well with the hypervirulent phenotypes, which call for a better definition and screening for these truly hypervirulent CR-HvKP strains in clinical settings.

目前，新近出现的碳青霉烯类耐药高毒力肺炎克雷伯菌（carbapenem-resistant hypervirulent Klebsiella pneumoniae, CR-HvKP）的流行病学特征及其对人类健康的潜在威胁仍不明确。本研究纳入2014—2017年从中国不同地理区域3家医院收集的784株携带blaKPC-2的碳青霉烯类耐药肺炎克雷伯菌（carbapenem-resistant Klebsiella pneumoniae, CRKP），对所有菌株开展分子分型、毒力质粒筛选与串珠试验，并对其中367株进行全基因组测序（whole genome sequencing, WGS）。2014—2017年间，中国临床分离的肺炎克雷伯菌中，CRKP的占比急剧升高。其中58%的CRKP菌株携带毒力编码质粒，但仅13%的菌株通过串珠试验与中性粒细胞试验表现出高毒力表型。研究发现，携带毒力质粒的CRKP菌株未表现出高毒力表型，系其rmpA与rmpA2基因发生突变导致功能失活所致；而部分携带野生型rmpA的菌株同样未表现出高毒力表型，这提示可能存在其他因素参与CRKP的高毒力调控。系统发育与单核苷酸多态性（single nucleotide polymorphism, SNP）分析结果显示，中国境内此类CRKP菌株的传播可能涉及ST11型（sequence type 11, ST11）的多个主要克隆谱系。携带IncFII型pSWU01样blaKPC-2质粒，是此类CRKP菌株产生碳青霉烯类耐药性的主要机制。综上，本研究数据表明，中国境内携带毒力质粒的CRKP菌株流行率快速上升，但遗传标记与高毒力表型之间的相关性较差，这要求在临床场景中建立更完善的定义与筛查方法，以精准识别真正的高毒力CR-HvKP菌株。