Experimental Klebsiella pneumoniae burn wound sepsis: role of capsular polysaccharide.

The role of Klebsiella pneumoniae capsular polysaccharide in relation to virulence in a murine burn wound sepsis model was investigated. Burn trauma markedly predisposed mice to lethal K. pneumoniae sepsis. A highly encapsulated variant (KP1-O) derived from K. pneumoniae KP1 was found to be extremely virulent for burned mice (50% lethal dose less than 10 organisms), whereas another variant (KP1-T), which possessed a much smaller capsule, was comparatively nonvirulent (50% lethal dose greater than 10(6) organisms). Production of large quantities of capsular material by KP1-O allowed for its rapid growth in vivo and persistence in the blood and liver. These traits were not demonstrated by KP1-T, which was effectively cleared after challenge.