Pathogenicity of a serotype 12:A Pasteurella multocida in hydrocortisone treated and nontreated rabbits.

A Pasteurella multocida isolate of 12:A serotype from a rabbit caused typical pulmonary pasteurellosis and death in pasteurella-free rabbits by intranasal exposure. Rabbits stressed with hydrocortisone and inoculated with 12:A Pasteurella multocida organisms developed a higher prevalence of pneumonia than rabbits not treated with hydrocortisone. Typical 12:A Pasteurella multocida was isolated from nasal cavity, trachea, and lungs and was most prevalent in nasal cavities. Surviving rabbits developed serum agar gel precipitating antibody beginning 15 days post-inoculation. The data showed that the 12:A Pasteurella multocida isolate was pathogenic, caused mortality, colonized the respiratory tract, and stimulated systemic immune response by producing serum agar gel precipitating antibody.