Background: The spread of carbapenem resistance among Klebsiella pneumoniae (K. pneumoniae) is a major public health problem, particularly in neonatal intensive care units (NICUs). Aim: To describe the nosocomial co-outbreak of ST37 and a new sequence type ST3006 K. pneumoniae, causing catheter-related bloodstream infections in NICU. Methods: Fifteen strains of K. pneumoniae were isolated from seven neonates during June 3-28, 2017, in a tertiary hospital neonatal intensive care unit in Fujian, China. Antimicrobial susceptibility was determined by the Vitek 2 system and micro-broth dilution method. Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used to analyse the genetic relatedness of isolates. Genome sequencing and gene function analyses were performed for investigating pathogenicity and drug resistance and screening genomic islands. Findings: Two K. pneumoniae clones were identified from seven neonates with multi-site infection, one ST37 strain and one new sequence type ST3006. Antimicrobial susceptibility testing revealed that the ST37 strain exhibited multi-drug resistance and carbapenem resistance. The ST3006 strain was only resistant to ampicillin-sulbactam, cefazolin, ceftriaxone. MLST and PFGE showed that 15 strains were divided into three groups, with a high level of homology. Gene sequencing and analysis indicated that KPN1343 harboured 12 resistance genes, 15 genomic islands and 205 reduced virulence genes. KPN1344 harboured four resistance genes, 19 genomic islands and 209 reduced virulence genes. Conclusion: Co-outbreak of K. pneumoniae involved two clones, ST36 and ST3006, causing multi-site infection. Genome sequencing and analysis is an effective method for studying bacterial resistance genes and their functions.

Co-outbreak of ST37 and a novel ST3006 Klebsiella pneumoniae from multi-site infection in a neonatal intensive care unit: a retrospective study