Role of lipopolysaccharide in virulence of Pseudomonas aeruginosa

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Abstract
The role of lipopolysaccharide (LPS) in the virulence of P. aeruginosa was studied. The virulence of several P. aeruginosa strains for burned mice was directly related to the dispersion of LPS into the phenol or the H2O phase after extraction. Virulence decreased as the proportion of LPS recovered from the phenol phase increased. No similar correlation was observed when several other strain characteristics were investigated. This phenomenon was studied in greater detail by using the smooth-specific phage E79 to select mutants altered in LPS structure. One such mutant, PA220-R2, was extensively characterized. LPS isolated from PA220-R2 was completely deficient in high-MW polysaccharide material. This alteration rendered the strain serum sensitive and dramatically changed the reaction with O-specific typing sera and sensitivity to typing phages. Motility, toxin A and elastase production, and 22 metabolic functions remained unchanged. PA220-R2 was comparatively nonvirulent, with a LD50 > 1000-fold higher than that of its parent for burned mice. This was due to the inability of PA220-R2 to establish an infection in burned skin.