Purpose: Severe infection has been the leading causes of neonatal death, especially the emergency of multidrug-resistant bacteria such as carbapenem-resistant Enterobacteriaceae. This study aimed to investigate the outbreak of carbapenem-resistant Klebsiella pneumoniae  (CR-KP) in neonatal wards and to explore the possible pathogenesis of Klebsiella pneumoniae .
Materials and Methods: CR-KP were collected from neonatal ward of Chongqing Health Center for Women and Children between 2017 and 2019. Broth microdilution method was used to evaluate the antimicrobial activities in vitro, at the same time, the virulence of the strain was evaluated by in vitro and in vivo experiments. At last, prokaryotic chain specific transcriptome sequencing was conducted to explore the possible pathogenesis of CR-KP.
Results: In this study, a total of 14 carbapenem-resistant-Klebsiella pneumoniae  (CR-KP) strains were isolated from Chongqing Health Center for Women and Children, among which all CR-KP isolates were identified as NDM-1-producers. Molecular epidemiological studies revealed ST147 being the most common sequence type (ST). Moreover, we first found two phenotypes of K. pneumoniae with different virulence from the same specimen. Type I, which was a white and sticky colony had a slight increase in virulence with higher biofilm formation, serum resistance and virulence than Type II with gray colony. Compared with the Type II, 10 pathways were obviously changed in Type I especially amino acid metabolism, such as arginine and proline metabolism.
Conclusion: Our findings revealed a new potential threat of NDM-1-positive CR-KP with higher virulence in neonatal ICU ward. We found two phenotypes of K. pneumoniae  with different virulent, which may be due to the difference expression of arginine and proline metabolism.
Keywords: neonates, carbapenem-resistant-Klebsiella pneumoniae , NDM-1, virulence