Pneumonia due to Pseudomonas aeruginosa occurs with increased frequency and high mortality in certain populations of patients. The potential of vaccination with a heptavalent lipopolysaccharide pseudomonas vaccine for specific protection of respiratory tissues from infection with Pseudomonas was evaluated with a guinea pig model of experimental pseudomonas pneumonia. Animals routinely responded to vaccination with a fourfold rise in titer of serum hemagglutinating antibody to Pseudomonas. Of 25 control animals, all but nine died after lung challenge with Pseudomonas, whereas vaccinated animals had a greater survival rate (22 of 25 animals survived; P less than 0.01). Rates of clearance of viable Pseudomonas from lung tissue were significantly greater in vaccinated animals than in controls during the first 6 hr after infection. Both gross and microscopic findings of lung tissue damage from pseudomonas pneumonia were less in vaccinated than in control animals. Thus, lipopolysaccharide pseudomonas vaccine appears to produce a local protective response in respiratory tissue against Pseudomonas.
