Bactericidal activity in the sera of mice vaccinated with Pasteurella multocida type A.

The susceptibility of Pasteurella multocida to killing by serum and the ability of protective vaccines to stimulate this mechanism of immunity in mice were investigated. P. multocida type of bovine origin was used to prepare a vaccine incorporating heat killed organisms and for homologous infection of mice. Bactericidal capacity and ELISA antibody titres were determined for individual mouse sera. Protection was clearly associated with bactericidal antibodies raised by vaccination. The bactericidal assay may be useful as a rapid, simple screening test of vaccinated mice for functional protective antibody levels.