Tandem Repeat of bla NDM-1 and Clonal Dissemination of a fosA3 and bla KPC-2 Co-Carrying IncR-F33: A-: B- Plasmid in Klebsiella pneumoniae Isolates Collected in a Southwest Hospital in China, 2010-2013.

Abstract

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has been widespread in coastal cities of eastern China since 2009. However, how CRKP spreads and evolves in southwest China is unclear. We investigated the genetic characteristics and dissemination mechanisms of carbapenemase genes in forty-one non-repetitive CRKP isolates collected from a southwest hospital, Kunming, Yunnan, during 2010-2013. Drug susceptibilities were analyzed by using VITEK 2 compact system. Genetic relationships were ascertained based on multilocus sequence typing (MLST) and Pulsed-field gel electrophoresis (PFGE) analysis. Genetic backgrounds of bla KPC-2 and bla NDM-1 were revealed by DNA walking and high-throughput sequencing. All isolates were highly resistant to common antibiotics except for tigecycline. In total, 34 bla KPC-2, 3 bla NDM-1, 1 bla IMP-4 and 3 bla IMP-26 genes were identified and KP67 plasmid 1 co-harbored bla NDM-1 and bla IMP-26. Five sequence types, namely ST11, ST290, ST340, ST395 and ST437, were recognized by MLST. Surprisingly, bla KPC-2 was only detected in ST11 strains. We described a clonal dissemination of fosA3-positive IncR-IncF33:A-:B- multireplicon plasmid carrying the gene cassettes IS26-ΔTn3-ISKpn27-bla KPC-2-ΔISKpn6-korC-klcA-ΔrepB-Tn1721 in all ST11 isolates. Three bla NDM-1 positive isolates belonged to three different ST types and their bla NDM-1 genetic backgrounds were also distinct. Interestingly, the flanking regions of bla NDM-1 in KP67 and KP72 were duplicated into one to five copies in a form of tandem repeat by the transposition of IS91 like element. The bla NDM-1 of KP82 was carried on a common IncX3 plasmid. This study described the early epidemiological characteristics of bla KPC-2/bla NDM-1-carrying CRKP, and reported a new tandem repeat pattern of bla NDM-1 cluster in Yunnan. These findings extend our knowledge on the carbapenemase gene evolutions.