Passive protection of mice against Pseudomonas aeruginosa by serum from recently vaccinated mice

Abstract

Serum of mice which had been inoculated 3 days previously with a vaccine (P14F1) prepared from a strain of Pseudomonas aeruginosa P14 gave passive protection to unvaccinated mice against a lethal i.p. challenge by Ps. aeruginosa P14. The serum which protected mice against Ps. aeruginosa P14 did not agglutinate suspensions of this organism. Its capacity to protect unvaccinated mice was removed by absorption with Ps. aeruginosa P14, but not by absorption with an unrelated strain of Ps. aeruginosa; passive protective capacity was removed also by absorption with a strain of Klebsiella aerogenes but not by absorption with a strain of Proteus mirabilis. Serum from recently vaccinated mice had no bactericidal activity against the immunizing strain; heparinized blood taken from such mice usually showed no bactericidal action, but there was consistently poorer growth of the pseudomonas in blood from recently vaccinated mice, or from mice passively protected by serum from the recently vaccinated, than in blood from unvaccinated mice.