Abstract
Background
To date, little is known about the virulence characteristics of pyogenic liver abscess (PLA) that cause multidrug resistant (MDR) Klebsiella pneumoniae (K. pneumoniae), which might be due to the rarity of these strains. This study aimed to analyze the virulence characteristics and molecular epidemiology of 12 MDR strains obtained from 163 PLA cases in a tertiary teaching hospital from the perspective of clinical characteristics, virulence phenotypes, and genotypes.
Methods
The MDR strains were obtained from sterile fluid samples collected from patients with PLA. The antimicrobial susceptibility testing was confirmed by the agar dilution method and microdilution broth method. The virulence phenotypes were analyzed by the growth curves, string test, capsular quantification, serum killing test, biofilm formation assay and infection model. Polymerase chain reaction (PCR) was used to investigate the virulence genotypes. The molecular epidemiology was identified by multilocus sequence typing (MLST).
Results
The results of growth curves, string test, capsular quantification, serum killing test, biofilm formation assay, and infection model revealed that the virulence phenotypes of the 12 PLA-causing MDR K. pneumoniae were similar to or more obvious than those of the typical hypervirulent K. pneumoniae strains. These MDR strains were mainly non-K1/K2 serotypes and carried multiple virulence genes. The results of MLST illustrated that the MDR strains were categorized into 9 sequence types.
Conclusions
This is the first study to analyze the virulence characteristics in PLA-causing MDR strains. The data revealed the coexistence of hypervirulence and MDR in PLA-causing MDR K. pneumoniae strains, and the clones of these strains were diverse and scattered. Also, one ST11 carbapenem-resistant hypervirulent strain was identified in PLA.