Microbiological characterisation of Klebsiella pneumoniae isolates causing bloodstream infections from five tertiary hospitals in Beijing, China.

OBJECTIVES: Klebsiella pneumoniae is prevalent in China. Little is known about the microbiological characteristics of clinical K. pneumoniae isolates causing bloodstream infections (BSIs).

METHODS: BSI-causing K. pneumoniae (BSI-Kpn) were collected from five tertiary-care hospitals in Beijing. Genetic relatedness was analysed by PFGE, antimicrobial susceptibility was determined by agar dilution, and sequence types (STs) were evaluated by MLST. Hypermucoviscosity (HV) phenotype was identified by positive string test. Carbapenemase, capsular serotype and HV-associated genes were detected by PCR.

RESULTS: A total of 219 non-duplicate BSI-Kpn were collected from December 2013 to December 2014 and were categorised into 203 types (strains) with unique PFGE patterns. Among 203 BSI-Kpn, 105 STs were identified. Overall, ST11 and ST23 were the predominant clones (14 strains each; 6.9%), followed by ST412 (n=13), ST37 (n=9), ST65 (n=7), ST15 (n=6), ST86 (n=6), ST592 (n=5) and ST29 (n=4). There were 74 STs containing only a single strain. Approximately 8.4% (17/203) of the strains exhibited carbapenem resistance, most producing KPC carbapenemase. The majority (75.9%; 154/203) of isolates were associated with non-K1/K2/K5/K20/K54/K57 serotypes. Only 16.3% (33/203) of the strains had K1/K2 serotypes. A total of 66 (32.5%) of the BSI-Kpn strains exhibited a HV phenotype. rmpA was a predominant factor in determining a HV phenotype.

CONCLUSIONS: The majority of BSI-Kpn strains exhibited high genetic diversity and low resistance to commonly used antimicrobials. The specific capsular serotype and HV phenotype were not major features of BSI-Kpn strains in China.