An outbreak of bla_KPC−4- and bla_VIM−1-producing Klebsiella pneumoniae and Klebsiella variicola at a single hospital in South Korea

Background: The dissemination of Klebsiella spp. producing multiple carbapenemases has been increasingly recognized. Between July 2019 and August 2021, ten patients were found to carry Klebsiella spp. co-harboring bla_KPC−4 and bla_VIM−1 across multiple wards at a Korean hospital, and one isolate was recovered from a hand-washing sink, more than a year after the outbreak. This study aimed to investigate the outbreak and conduct a genomic study of these isolates. Methods: Whole-genome sequencing, including long-read sequencing, was performed to analyze plasmid structures and mobile genetic elements (MGEs). Bioinformatics analyses were performed to trace clonal transmission chains and horizontal gene transfer. Results: The findings suggested that the inter-ward spread of Klebsiella spp. seemed to be facilitated by healthcare worker contact or patient movement. Of the nine isolates collected (eight clinical and one environmental), seven (including the environmental isolate) were identified as K. pneumoniae (ST3680) and two were K. variicola (single-locus variant of ST5252). These isolates showed high genetic relatedness within their species and harbored the IncHI5B plasmid carrying both bla_KPC−4 and bla_VIM−1 (pKPCVIM.1). On this plasmid, bla_VIM−1 was located in the Class 1 integron associated with IS1326::IS1353 (In2), and Tn4401b carrying bla_KPC−4 was inserted into IS1326::IS1353, creating a novel MGE construct (In2_bla_VIM−1-Tn4401b_bla_KPC−4). Conclusion: The hospital-wide spread of bla_KPC−4 and bla_VIM−1 was facilitated by clonal spread and horizontal plasmid transfer. The persistence of this strain in the hospital sink suggests a potential reservoir of the strain. Understanding the transmission mechanisms of persistent pathogens is important for improving infection control strategies in hospitals.