Pseudomonas aeruginosa infection and vaccination in the rat.

A large molecular-weight fraction of Pseudomonas aeruginosa culture filtrate protected rats and mice against a lethal infection with a heterologous serotype, and to some extent against Escherichia coli and Listeria monocytogenes. The active components were obtained from cultures grown for several days in a simple synthetic medium. Infection and vaccination with P. aeruginosa serotype 16 induced agglutinating and precipitating antibodies to the components of this serotype only; in rats infected or vaccinated with serotype 1, low titres of agglutinating antibody against type 16 were found. Vaccine prepared from type 1 or 16 increased, within 3 days of infection, the resistance of rats to type-16 organisms; within the same period agglutinins or precipitins were not produced. It is possible that the protection was based on opsonic and antitoxic activities.