Seroepidemiology of Klebsiella pneumoniae in an Australian Tertiary Hospital and its implications for vaccine development

Abstract

The aim of this study was to determine the diversity of Klebsiella pneumoniae capsular serotypes in an Australian setting. Consecutive (n = 293) nonrepetitive isolates of K. pneumoniae from a large teaching hospital laboratory were analyzed. The majority of isolates were from urinary specimens (60.8%); the next most common source was sputum (14.3%), followed by blood (14%). Serotyping revealed a wide range of capsule types. K54 (17.1%), K28 (4.1%), and K17 (3.1%) were the most common, and K54 isolates displayed a high degree of clonality, suggesting a common, nosocomial source. In vitro, one K54 isolate was more adherent to urinary catheters and HEp-2 cells than four other tested isolates; it was slightly more resistant to chlorhexidine but was more susceptible to drying than heavily encapsulated strains. This is the first seroprevalence survey of K. pneumoniae to be performed on Australian isolates, and the high level of diversity of serotypes suggests that capsule-based immunoprophylaxis might not be useful for Australia. In addition there are significant differences in the predominance of specific serotypes compared to the results of surveys performed overseas, which has important implications for capsule-based immunoprophylaxis aimed at a global market.

FIG. 1.

PFGE of 20 K. pneumoniae serotype K54 isolates (18 from nosocomial infections) from different individuals. Eighteen isolates are closely related (having fewer than three bands of difference), indicating clonality. Lane 4 has up to four bands and lane 6 more than six bands different from the other lanes. Lanes 1, 7, 13, 19, and 25 show molecular markers in 48.5-kb increments.

FIG. 2.

Histogram representing the number of bacteria adherent to HEp-2 cells for five strains of K. pneumoniae, expressed as a percentage of the initial inoculum for each strain (log scale). The K54 strain was significantly (*, P < 0.005) more adherent than the other four strains.

FIG. 3.

Histogram representing the number of bacteria adherent to 0.5-cm sections of urinary catheter of five strains of K. pneumoniae after 3 h of incubation. The data for adherent bacteria are expressed as a percentage of the initial inoculum for each strain (log scale). The K54 strain was significantly (*, P < 0.005) more adherent than the other four strains.

FIG. 4.

Histogram representing the number of bacteria recovered after drying five strains of K. pneumoniae for 1 h, 4 h, and 24 h. After 1 h of drying strain B5055 was significantly (*, P < 0.005) more resistant to drying than the K54 and K1 strains, and at 4 and 24 h B5055 was significantly (**, P < 0.005) more resistant to drying than the other four strains.