Abstract: Objective To investigate the resistance mechanisms of Carbapenem-resistant Klebsiella pneumonia by genetic analysis, virulence features, phenotypic methods and homology isolated from blood samples. Methods A total of 23 Carbapenem-resistant Klebsiella pneumoniae strains were isolated from blood culture samples between January 2018 and December 2019. Hypervirulent strains and capsular serotypes were identified by string test and Wzi gene sequencing respectively. The exopolysaccharide synthesis regulator gene (rmpA), virulence- associated genes and carbapenemase genes were detected by PCR method. Multilocus sequence typing was used to analyze phenotype of strains. Pulsed field gel electrophoresis was used to analyze the homology of strains. Results All 23 strains of Klebsiella pneumoniae carried KPC-2 genes. There were 18 strains showed positive results of string test and rmpA. Wzi gene sequencing results showed that 22 strains were K14.64 type and 1 strains was K19. All 23 strains were divided into 3 groups by multilocus sequence typing , with the results of ST11 (18/23), ST307 (4/23) and ST15 (1/23). We further identified 18 ST11 strains into three types by pulsed field gel electrophoresis. Conclusions The resistance to carbapenem of Klebsiella pneumoniae strains was mainly associated with KPC-2 gene, which main serotype of capsule was K14.64 and dominant sequence type was ST11 type.

Key words: Carbapenem resistantant Klebsiella pneumoniae, Virulence factors, Multilocus sequence typing Homology