Abstract
Cell envelope proteins and lipopolysaccharides (LPS) of Pasteurella multocida strains associated with atrophic rhinitis in swine were compared by using sodium dodecyl sulfate gel electrophoresis. Among 34 strains, three different types of cell envelope protein patterns, named I (16 strains), II (3 strains), and III (15 strains), could be distinguished. These differences were based on the electrophoretic mobility of the major protein, designated as protein H. Comparison of cell envelope protein type and pathogenicity of the strain, the latter property predicted by the guinea pig skin test, revealed that all type I strains, 6 of 15 type III strains, and none of the type II strains were pathogenic. Although pathogenicity has been correlated with extracellular toxin activity, no protein could be detected in either the cell envelopes or in the extracellular fluid that absolutely correlated with pathogenic strains. Electrophoretic analysis of the LPS revealed that all strains possessed low-molecular-weight LPS, which is inconsistent with the presence of a classical O antigen. The method allowed the detection of at least six types of LPS, which often coincided with a certain cell envelope protein type and with the presence or absence of the pathogenic character of the strain. These results strongly suggest that the sampled swine carry a limited number of P. multocida clones, in each of which the patterns of cell envelope proteins and LPS, as well as the presence or absence of the ability to produce extracellular toxin, are well conserved. Therefore, the possibility is discussed that sodium dodecyl sulfate gel electrophoresis of cell envelope proteins and LPS may be used for the prediction of the pathogenic character of part of the strains. Finally, the typing of strains based on cell envelope protein patterns might contribute to the development of vaccines containing outer membrane proteins as protective antigens.