Identification and Characterization of NDM-1-producing Hypervirulent (Hypermucoviscous) Klebsiella pneumoniae in China

Background: Carbapenem-resistant hypervirulent (hypermucoviscous) Klebsiella pneumoniae (CR-HMKP) poses a significant public health challenge. We investigated its epidemiology and molecular characteristics in a tertiary care hospital in eastern China. Methods: CR-HMKP were identified among 106 non-duplicated carbapenem-resistant K. pneumoniae isolates (from June 2013 to September 2017) using the string test. The pulsotype (PT) and sequence type (ST) of CR-HMKP isolates were determined using pulsed-field gel electrophoresis and multilocus sequence typing. Resistance determinants, capsular serotypes, and virulence genes were detected by PCR and sequencing. Representative isolates from each PT were selected, and their virulence phenotypes were established using the serum killing and Galleria mellonella lethality assays. Results: Of the 106 isolates, 13 (12.3%) were CR-HMKP. Seven were positive for bla(NDM-1) and shared the same genotype (PT5/ST1764); the others were positive for bla(KPC-2), belonged to ST11, and were divided into four different PTs. The serotype of all bla(NDM-1)-positive isolates was K64, while that of bla(KPC-2)-positive isolates were K47 (N=4) and K64 (N=2). The NDM-1-producing HMKP isolates were positive for aerobactin, exhibited high serum resistance, and elicited significantly increased larval mortality compared with the other isolates. All patients had received invasive treatment prior to infection by NDM-1-producing HMKP. The infections occurred between July and August 2016 and were hospital-acquired. Conclusions: NDM-1-producing HMKP ST1764 isolates were identified; this is the first report worldwide on an outbreak of nosocomial infection caused by these isolates. Effective surveillance and strict infection control strategies should be implemented to prevent CR-HMKP dissemination.