Seroepidemiology of Klebsiella bacteremic isolates and implications for vaccine development

The frequencies of capsular serotypes among 703 Klebsiella strains isolated from the blood of hospitalized patients were determined. More than 90% of the isolates were typeable, with 69 of the 77 known serotypes being identified. Serotypes 2, 21, and 55, representing 8.9, 7.8, and 4.8% of all the isolates, respectively, were observed at a frequency significantly higher (P less than 0.05) than that for other capsular serotypes. Approximately 43% of the serotypes appeared at a frequency of less than 0.5%. Differences were found when the seroepidemiology of North American and European isolates was compared. The current findings indicate that a capsular polysaccharide-based vaccine against Klebsiella organisms is feasible and should be multivalent, eliciting antibodies directed against the 25 serotypes which make up approximately 70% of all the bacteremic isolates.