Clinical and molecular characteristics of bloodstream infection caused by K. pneumonia

Abstract

Objective To investigate the clinical features and molecular characteristics of bacteremia caused by K. pneumoniae and study on the differences between classical and hypervirulent K. pneumonia(hvKP). Methods The clinical features of 70 cases of K. pneumoniae bacteremia collected from Beijing Chaoyang Hospital from 2008 to 2012 were retrospectively analyzed. The patients were identified according to the records from the Clinical Microbiology Department. Patients' data were obtained from medical records. The molecular characteristics of the K. pneumoniae strains were also studied using PCR, multilocus sequence typing and pulsed field gel electrophoresis(PFGE) methods. Data were analyzed using the statistical package SPSS for windows version 17.0. For categorical data, different groups were compared using the Chi-square test to analyze the quantitative variables. P≤0.05 was considered to be statistically significant. All susceptibility data were analyzed using Whonet, version 5.6. Results The hvKP was identified from 31.4% of the patients with K. pneumoniae bacteremia, which displayed 4 serotypes (K1, K2, K20, and K57). About 40.9% (9/22) hypervirulent strains were isolated from patients without underlying diseases, while 95.8% (46/48) of the classic K. pneumoniae infections were found in patients with the presence of one or more underlying diseases. More hvKP positive patients (95.5%, 21/22) had community-acquired infections compared with classical K. pneumonia (cKP) infected patients (35.4%, 17/48). There was a significant difference between these two groups (χ2=21.912, P<0.001). Two ESBLs-producing hvKP strains were found. The 22 hvKP isolates had 14 different PFGE patterns, among which 6 isolates (patients with primary liver abscess) shared similar PFGE patterns. Conclusions The emerging hvKP was prevalent in patients with severe community-acquired infections in healthy individuals. Two ESBLs-producing hvKP strains were identified. Drug resistance had a rising trend, which called for more attention in clinical settings. (Chin J Lab Med, 2015, 38: 627-631) Key words: Liver abscess; Community-acquired infections; Klebsiella pneumoniae; Virulence