Edward Wai‐Chi Chan

The increasing incidence of carbapenem-resistant Enterobacteriaceae (CRE) -mediated hospital infections in China prompted a need to investigate the genetic basis of emergence of such strains. A nationwide survey was conducted in China covering a total of 1105 CRE strains collected from 25 geographical locales with results showing that acquisition of two carbapenemase genes, bla KPC-2 and bla NDM , was responsible for phenotypic resistance in 90% of the CRE strains tested (58% and 32% respectively), among which several major strain types, such as ST11 of K. pneumoniae and ST131/ST167 of E. coli, were identified, suggesting that dissemination of specific resistant clones is mainly responsible for emergence of new CRE strains. Prevalence of the fosA3 gene which mediates fosfomycin resistance, was high, while the colistin resistance determinant mcr-1 was rarely present in these isolates. Consistently, the majority of the bla NDM -bearing plasmids recoverable from the test strains belonged to IncX3, which contained a common core structure, bla NDM -blaMBL-trpF. Likewise, the core structure of ISKpn27bla KPC-2 -ISKpn2 was observed among plasmids harboring the bla KPC-2 gene, although they were genetically more divergent. In conclusion, the increasing prevalence of CRE strains in China is attributed to dissemination of conservative mobile elements carrying bla NDM or bla KPC-2 on conjugative and non-conjugative plasmids.

Members of the genus Klebsiella have rapidly evolved within the past decade, generating organisms that simultaneously exhibit both multidrug resistance and hypervirulence (MDR-hv) phenotypes; such organisms are associated with severe hospital- and community-acquired infections. Carbapenem-resistant infections with unknown optimal treatment regime were of particular concern among the MDR-hv Klebsiella strains. Recent studies have revealed the molecular features and the mobile resistance elements they harbour, allowing identification of genetic loci responsible for transmission, stable inheritance, and expression of mobile resistance or virulence-encoding elements that confer the new phenotypic characteristics of MDR-hv Klebsiella spp. Here, we provide a comprehensive review on the taxonomic position, species composition and different phylotypes of Klebsiella spp., describing the diversity and worldwide distribution of the MDR-hv clones, the genetic mutation and horizontal gene transfer events that drive the evolution of such clones, and the potential impact of MDR-hv infections on human health.