Variation in outer-membrane protein and lipopolysaccharide profiles of Pasteurella haemolytica isolates of serotypes A1 and A2 obtained from pneumonic and healthy cattle.

Abstract

The outer-membrane protein (OMP) and lipopolysaccharide (LPS) profiles of 29 isolates of Pasteurella haemolytica serotypes A1 (18 isolates) and A2 (11 isolates), obtained from pneumonic (13 isolates) or healthy (16 isolates) cattle, were compared by SDS-PAGE and Western blot analysis. Coomassie-blue-stained OMP profiles of serotype A1 and A2 isolates could be distinguished from each other by differences in both major and minor proteins. Whereas the OMP profiles of the serotype A1 isolates were extremely uniform in stained gels, there was variation in the mobilities of high-molecular-mass minor proteins and one of the major proteins of serotype A2 isolates. Differences in the OMP profiles of isolates within both the A1 and A2 serotypes were more clearly distinguished by Western blotting than by staining after SDS-PAGE. Thus, by Western blot analysis, four distinct OMP profiles were identified within the serotype A1 and A2 isolates, respectively. The profiles of the serotype A1 isolates were designated OMP types 1.1, 1.2, 1.3 and 1.4; those of the serotype A2 isolates were designated OMP types 2.1, 2.2, 2.3 and 2.4. Three distinct LPS profiles were recognized among the isolates which, by comparison with previously described LPS types, were identified as smooth LPS type 1 and rough LPS types 3 and 5. Isolates of serotype A1 consisted of LPS type 1 only. whereas isolates of serotype A2 consisted of LPS types 3 or 5. OMP and LPS analysis of P. haemolytica has applications in epidemiological and virulence studies.