Objective: To conduct epidemiological analysis of Klebsiella pneumoniae (K. pneumoniae ) with hypervirulence , and to investigate its drug resistance phenotype, Extended-spectrum β-lactamase (ESBLs ) gene, virulence factor, capsular serotype and biofilm formation, so as to provide theoretical basis for further understanding of the drug resistance mechanism of K. pneumoniae with hypervirulence .
Methods: K. Pneumoniae were isolated from clinical samples collected from inpatients. All strains were identified by VITEK2 Compact using fully automatic microbial analyzer, the minimal inhibitory concentration (MIC ) of antibiotics was determined by microbroth dilution test. The double disk diffusion method was used to detect the production of ESBLs , modified carbapenem inactivation method (mCIM ) was used to detect the production of carbapenemase , and hypermucoviscosity phenotype was detected by wire drawing test. PCR was used to detect ESBLs gene, virulence factor and capsular serotype. Crystal violet staining was used to detect the ability of biofilm formation.
Results: The ESBLs genes detected in this study included strains blaTEM 35 (36.5%), blaSHV 51 (53.1%), and blaCTX-M 49 (51.0%). Most strains carried multiple ESBLs genes , but not all of them produce ESBLs. K1 and K2 accounted for 14.6% and 11.5% respectively. Most (91.7%) strains carried the fimH gene, and the other virulence genes were ybtS (53.1%), entB (46.9%), rmpA (41.7%), aerobactin (32.3%), allS (15.6%), kfu (15.6%). Of all the Klebsiella pneumoniae strains, 33 (34.4%) exhibited ESBLs phenotype, 16 (16.7%) were carbapenemase-producing, and 20 (20.8%) with ESBLs phenotype tested were resistant to all four drugs. The correlation between ESBLs-producing strains and biofilm formation was significantly increased compared to strains without ESBLs phenotype (P =0.035).
Conclusion: Compared to hypervirulent Klebsiella pneumoniae (hvKP ), classical Klebsiella pneumoniae (cKP ) has a tendency to acquire antibiotic resistance. Our study showed that genes encoding rmpA, K1 or K2 , and kfu were highly associated with hvKP .
Keywords: Klebsiella pneumoniae , antimicrobial resistance, hypermucoviscosity, virulence factors, epidemiology