Molecular epidemiology of extensively drug-resistant Klebsiella pneumoniae outbreak in Wenzhou, Southern China

The emergence of extensively drug-resistant (XDR) Klebsiella pneumoniae has become a major challenge worldwide. In this study, we characterized the phenotypes and genetic features of nine XDR K. pneumoniae isolates from an integrated hospital in Zhejiang province, China, from September to October 2014. These XDR K. pneumoniae possessed at least five resistance determinants which contribute to highly resistant to beta-lactam, beta-lactam/inhibitor combinations, aminoglycosides, quinolones, carbapenems, chloroamphenicol and fosfomycin. All isolates carried bla(KPC-2), bla(CTX-M-9), bla(SHV-11) and rmtB, and several isolates also harboured bla(TEM-1) and qnrS. Southern blot experiments confirmed that bla(KPC-2), rmtB and bla(CTX-M-9) were located on the same similar to 54.2 kb plasmid. Conjugative plasmids were obtained from all K. pneumoniae isolates, further proving the transferable characteristic of the resistance determinants. The OmpK36 sequences showed various deletions and insertions that indicated additional amino acid residues and a deleted phenotype of OmpK36. PFGE demonstrated that all the isolates belonged to the same genotype. Multilocus sequence typing was concordant with PFGE results and revealed that ST11 was the most predominant clone. Our study revealed a high incidence and endemic spread of XDR K. pneumoniae in the hospital. Thus, effective infection control measures should be adopted to monitor and control the spread of multidrug-resistant isolates.