Outbreak of KPC-producing Klebsiella pneumoniae ST15 strains in a Chinese tertiary hospital: resistance and virulence analyses

Abstract

Background Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major cause of clinical infection. However, KPC-producing K. pneumoniae ST15 strains are occasionally identified and have never been reported to cause hospital outbreaks in China. Methods In this study, pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS) were used to characterize 32 KPC-producing K. pneumoniae ST15 strains, which were collected at a Chinese tertiary hospital. Susceptibilities, resistance genes, virulence factors and clinical performances of the ST15 strains were comparatively analysed with corresponding ST11 strains. Results The ST15 strains were distributed in 7 wards, mainly in the intensive care unit (ICU, 24/32, 75%). PFGE results from 24 strains covering all the wards presented a similarity of more than 92%, indicating clonal spread. In 84% of the ST15 strains, the imipenem (IPM) and meropenem (MEM) minimum inhibitory concentrations (MICs) were ≤ 8 and ≤ 16 µg/mL, respectively, both of which were 4-fold lower than those of the ST11 strains. The infection rates of the ST15 and ST11 strains were 28.1% and 43.9%, respectively (P = 0.018). PCR evaluation and WGS indicated that all the CRKP strains shared a 100% identical blaKPC−2 genetic structure, though a synonymous mutation and a Gly115-Asp116 (GD) insertion in the OmpK36 were identified in the ST15 and ST11 strains, respectively. None of the ST15 strains were positive for hypervirulence factors; however, the positive rate was 92.7% (38/41) in the ST11 isolates. Conclusion To the best of our knowledge, this is the first description of nosocomial outbreaks caused by KPC-producing K. pneumoniae ST15 strains in China. The ST15 strains had low carbapenem resistance and virulence, emphasizing the importance of careful evaluation of phenotypic and genetic characteristics for anti-infection therapy.