Effect of aerosol immunization with RE 595 Salmonella minnesota on lung bactericidal activity against Serratia marcescens, Enterobacter cloacae, and Pseudomonas aeruginosa.

Intrapulmonary bactericidal activity was measured after mice were given 3 weekly aerosol exposures to acid-hydrolyzed Re 595 Salmonella minnesota. Ten days after their last immunization, mice were challenged with aerolized Serratia marcescens, Enterobacter cloacae, or Pseudomonas aeruginosa. Quantitative bacterial counts in ground lung were obtained immediately after exposure and again 4 hours later. Enhanced bactericidal activity against Serratia marcescens and Enterobacter cloacae was seen in immunized animals, whereas no difference with Pseudomonas aeruginosa was noted. In separate studies, immunization with Serratia marcescens yielded a similar enhancement of lung bactericidal activity. Mucociliary transport, as measured by disappearance of aerosolized Serratia marcescens labeled with phosphorus-32, was identical for both immunized and control animals. Using a standardized in vitro mouse alveolar macrophage phagocytic system, lung washes from animals immunized with Re 595 Salmonella minnesota had significant opsonic activity for Serratia marcescens but not for Pseudomonas aeruginosa.