VARIATION IN OUTER-MEMBRANE PROTEIN AND LIPOPOLYSACCHARIDE PROFILES OF PASTEURELLA-HAEMOLYTICA ISOLATES OF SEROTYPES A1 AND A2 OBTAINED FROM PNEUMONIC AND HEALTHY CATTLE

The outer-membrane protein (OMP) and lipopolysaccharide (LPS) profiles of 29 isolates Pasteurella haemolytica serotypes A1 (18 isolates) and A2 (11 isolates), obtained from pneumonic (13 isolates) or healthy (1 6 isolates) cattle, were compared by SDS-PAGE and Western blot analysi s. Coomassie-blue-stained OMP profiles of serotype A1 and A2 isolates could be distinguished from each other by differences in both major an d minor proteins. Whereas the OMP profiles of the serotype A1 isolates were extremely uniform in stained gels, there was variation in the mo bilities of high-molecular-mass minor proteins and one of the major pr oteins of serotype A2 isolates. Differences in the OMP profiles of iso lates within both the A1 and A2 serotypes were more clearly distinguis hed by Western blotting than by staining after SDS-PAGE. Thus, by West ern blot analysis, four distinct OMP profiles were identified within t he serotype A1 and A2 isolates, respectively. The profiles of the sero type A1 isolates were designated OMP types 1.1, 1.2, 1.3 and 1.4; thos e 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 isolate s which, by comparison with previously described LPS types, were ident ified as smooth LPS type 1 and rough LPS types 3 and 5. Isolates of se rotype A1 consisted of LPS type 1 only, whereas isolates of serotype A 2 consisted of LPS types 3 or 5. OMP and LPS analysis of P. haemolytic a has applications in epidemiological and virulence studies.