Emerging carbapenem-resistant Klebsiella pneumoniae ST16 causing multiple outbreaks in a tertiary hospital in southern Vietnam

The emergence of carbapenem resistance in Klebsiella pneumoniae represents a major global public health concern. Nosocomial outbreaks caused by Klebsiella pneumoniae are commonly reported to result in high morbidity and mortality due to limited treatment options. Between October 2019 and January 2020, two concurrent high mortality nosocomial outbreaks occurred in a referral hospital in Ho Chi Minh City. We performed genome sequencing and phylogenetic analysis of eight K. pneumoniae outbreak isolates and two environmental isolates for outbreak investigation. The two outbreaks were caused by two distinct lineages of the international ST16 clone, both of which displayed extensive drug resistance including resistance to carbapenem and colistin. Carbapenem-resistant ST16 outbreak strains clustered tightly with previously described ST16 K. pneumoniae, suggesting local persistence and rapid transmission of this particular clone across hospitals in Vietnam. We found environmental isolates from a hospital bed and blood pressure cuff that were genetically linked to an outbreak case cluster, showing the importance of high-touch surfaces as sources for nosocomial spread of K. pneumoniae. Further, we found colistin resistance caused by disruption of the mgrB gene by an ISL3-like element and carbapenem resistance mediated by a transferable IncF/blaOXA-181 plasmid carrying the ISL3-like element.