Inactivation of Pasteurella multocida within the mouse peritoneal cavity.

Normal ICR mice were injected intraperitoneally with 0.5 ml of thioglycollate broth or 5 x 10(8) heat-killed Pasteurella multocida vaccine and the number of polymorphs, lymphocytes and macrophages in the peritoneal washout suspensions were determined at intervals up to 72 hours. The stimulated mice were challenged intraperitoneally with opsonized or unopsonized P. multocida at increasing time intervals and the rate of growth by the organisms in the washout suspension was determined up to 60 minutes later. The opsonized bacilli were taken up by the 6 hr. exudate cells (50-60% PMNs) and their growth inhibited more effectively than when the 72 hr exudate cells were tested (only 10% PMNs). When the challenge inoculum was introduced into the peritoneal cavities of mice stimulated 6 hrs previously with 5 x 10(8) heat-killed P. multocida vaccine, up to 80% of the bacilli were inactivated over a 30 minute period. However, when 72 or 250 hr peritoneal exudate cells were tested, the inoculum was not inactivated, but showed an increasingly lethal effect.