Background: Patients with neurological disorders were easier to develop severe intracranial infections caused by hypervirulent and carbapenem-resistant K. pneumoniae , leading to a distressing clinical outcome. In this study, eight hv-CRKP were isolated from neurological patients, to clarify the resistant and virulent features.
Methods: We tested the susceptibility of common antibiotics in these isolates to feature the antibiotic-resistant phenotypes. We also detected the key virulence factors, including mucoviscosity, siderophores production, biofilm formation in vitro, and further evaluated the virulence potential with serum killing model. We also used whole-genome sequencing (WGS) to investigate the molecular mechanisms.
Results: We observed that ST11-KL64 hv-CRKP (6/8) has an overwhelming epidemic dominance in these hypervirulent and carbapenem-resistant K. pneumoniae . Though the acquirement of virulence plasmid made no influence to the maintain of multidrug-resistant phenotype of these isolates, only the ST11-KL64 strains fully exhibited the hypervirulent features. Compared with ST11-KL47 and ST15-KL24 strains, ST11-KL64 hv-CRKP were more advantages in productions of capsule polysaccharide, biofilm, and siderophores. The virulence potential of ST11-KL64 hv-CRKP was further confirmed by using serum killing model. Previous studies have demonstrated that IncFII plasmid could act as a helper plasmid to mobile the non-conjugative IncFIB/IncHIB virulence plasmids. We could only observe the co-existence of IncFII resistance plasmid and IncFIB/IncHIB virulence plasmids in ST11-KL64 isolates. The co-existence of such two plasmids facilitated the formation of ST11-KL64 hv-CPKP, which then become nosocomial epidemic under the antibiotic stress.
Conclusion: Overall, we observed the ST11-KL64 hv-CRKP dominated in the isolates from neurological patients, and required most clinical attention.
Keywords: Klebsiella pneumoniae  KPC-2, virulence plasmid, carbapenem resistance, hypervirulent