ABSTRACT
The distribution of a monoclonal antibody (MAb)-recognized protective protein immunogen on the outer membrane of 153 Pasteurella multocida rabbit isolates was determined by dot blot (DB) analysis. MAb 1608 reacted with 36 (24%) of the 153 clinical isolates. The DB-positive clinical isolates expressed capsular antigens A, D, and nontypable and somatic antigens 2, 3, 10, 12, 15, and nontypable. Western blot (immunoblot) analysis with adsorbed and eluted MAb 1608 confirmed that the antigenic determinant identified was located on the cell surface. With MAb 1608 as a probe for antibody-accessible radioimmunoassay, 31 of 36 DB-positive P. multocida rabbit isolates were shown to have surface-exposed and antibody-accessible antigenic determinants, while 44 of 44 DB-negative isolates were negative by antibody-accessible radioimmunoassay. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed DB-negative P. multocida isolates both with (6 of 13, 46%) and without (7 of 13, 54%) the 37.5-kilodalton protein. This study establishes that the protective antigenic determinant of the 37.5-kilodalton outer membrane protein is present in 24% of rabbit clinical isolates tested and is detectable in P. multocida strains distributed among the major somatic types (3, 10, 12, and 15) and the capsular types (A and D) commonly isolated from rabbits in North America.
