Intra-specific diversity within Pasteurella haemolytica was assessed by analysing variation in the capsular polysaccharide (serotypes), lipopolysaccharide (LPS) and outer-membrane proteins (OMPs) of 184 isolates recovered from cattle and sheep. Four of 12 serotypes comprised 83% of the total number of isolates, including A1 and A2 as the most frequently recovered serotypes from cattle and sheep, respectively. Nine distinct LPS profiles were identified. Four different core-ol igosaccharide patterns were present, each of which occurred alone as rough LPS and also in association with a single 0-antigen profile as smooth LPS; the ninth LPS type was also smooth but had a different O-antigen profile. The capsular serotypes could be divided into four groups based on the dominant LPS profile within each serotype: (1) Al, A6, A9, A12 and A5; (2) A2, A8, A14 and A16; (3) A7 and A13; and (4) A l l . Smooth LPS of type IA, which was found only in the first group, was associated primarily with bovine disease isolates, whereas rough LPS of types 1B and 3B were associated primarily with the group 2 serotypes and ovine disease isolates. Similarly, the variation of OMP profiles generated three groups: (1) Al, A6, A9, A12, A5 and A8; (2) A2, A14 and A16; and (3) A7, A l l and A13. Isolates belonging to groups 2 and 3 exhibited greater diversity in their OMP profiles than those belonging to group 1. Although the majority of group 3 isolates possessed profiles unique to that group, a smaller number of A7 isolates possessed profiles with similarities to those of serotypes A1 or A2. OMP profiles clearly differentiated bovine from ovine isolates of the same serotypes. The association both of specific LPS and OMP profiles with bovine or ovine disease isolates suggested a correlation between specific cell-surface structures and host specificity. The combined analysis of capsular serotypes, LPS types and OMP profiles identified seven major groups within P. haemolytica which were responsible for 59% of the disease cases, suggesting a clonal structure for this species. Overall, comparison of the capsular serotypes, LPS types and OMP profiles proved extremely useful for assessing diversity within P. haemolytica.

Bacteria resembling two Bordetella species were isolated from both normal and pneumonic ovine lungs using a selective charcoal agar. Twenty-eight of the 33 isolates showed similarities to stock NCTC B. parapertussis strains in their SDS-PAGE gel protein profiles, in their biochemical reactions and in causing browning on tyrosine agar. Five isolates behaved similarly to stock B. bronchiseptica strains, in being actively motile, in giving identical positive reactions in three out of four biochemical tests and in causing no colour change in tyrosine agar. Multilocus enzyme electrophoresis separated the isolates into two electrophoretic types distinguishable from those of stock B. parapertussis and stock B. bronchiseptica strains.

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