Capsular Polysaccharide Types and Virulence-Related Traits of Epidemic KPC-Producing Klebsiella pneumoniae Isolates in a Chinese University Hospital

Klebsiella pneumoniae is an important human pathogen associated with a variety of diseases and the prevalence of blaKPC carrying K. pneumoniae (KPC-Kp) is rapidly increasing. Capsule is an important virulence factor in K. pneumoniae. In this study, we determined to first systematically characterize capsular polysaccharide (CPS) and virulence traits in KPC-Kp strains. A total of 56 KPC-Kp isolates were recovered from clinical samples in a Chinese hospital, which were assigned to clonal lineages by multilocus sequence typing (MLST). Capsule typing (wzi sequencing and wzc polymerase chain reaction [PCR]) and virulence genes were characterized by molecular approaches. The virulence of these strains was determined by biofilm formation, serum killing resistance, phagocytosis, and infection models. Six different STs were found among 56 KPC-Kp isolates: 76.8% (43 of 56 isolates) belonged to ST11, 6 isolates belonged to ST147, 4 isolates belonged to ST15, 1 isolate belonged to ST1456, 1 isolate belonged to ST65, and 1 isolate was ST23. Based on the wzi gene DNA sequences and wzc PCR, these 56 strains were classified as capsular type wzi47-K47 (n = 37), wzi64-K64 (n = 8), wzi8-K8 (n = 4), wzi37-K37 (n = 4), wzi53-K53 (n = 1), wzi125-K2 (n = 1), and wzi1-K1 (n = 1). Heterogeneity was detected in biofilm formation and phagocytosis among different CPS types. ST11 strains were less virulent than other ST strains. KPC-Kp strains exhibit variability of virulence-associated traits. Differences were associated with the ST types and CPS.