INTRA-SPECIFIC DIVERSITY AND HOST-SPECIFICITY WITHIN PASTEURELLA-HAEMOLYTICA BASED ON VARIATION OF CAPSULAR POLYSACCHARIDE, LIPOPOLYSACCHARIDE AND OUTER-MEMBRANE PROTEINS

Intra-specific diversity within Pasteurella haemolytica was assessed b y analysing variation in the capsular polysaccharide (serotypes), lipo polysaccharide (LPS) and outer-membrane proteins (OMPs) of 184 isolate s recovered from cattle and sheep. Four of 12 serotypes comprised 83 % of the total number of isolates, including Al and AZ as the most freq uently recovered serotypes from cattle and sheep, respectively. Nine d istinct LPS profiles were identified. Four different core-oligosacchar ide patterns were present, each of which occurred alone as rough LPS a nd also in association with a single O-antigen profile as smooth LPS; the ninth LPS type was also smooth but had a different O-antigen profi le. The capsular serotypes could be divided into four groups based on the dominant LPS profile within each serotype: (1) Al, As, A9, A12 and A5; (2) AZ, A8, A14 and A16; (3) A7 and A13; and (4) All. Smooth LPS of type 1A, which was found only in the first group, was associated pr imarily with bovine disease isolates, whereas rough LPS of types in an d 3B were associated primarily with the group 2 serotypes and ovine di sease isolates. Similarly, the variation of OMP profiles generated thr ee groups: (1) Al, A6, A9, A12, A5 and A8; (2) AZ, A14 and A16; and (3 ) A7, All and A13. Isolates belonging to groups 2 and 3 exhibited grea ter diversity in their OMP profiles than those belonging to group 1. A lthough the majority of group 3 isolates possessed profiles unique to that group, a smaller number of A7 isolates possessed profiles with si milarities to those of serotypes Al or AZ. OMP profiles clearly differ entiated bovine from ovine isolates of the same serotypes. The associa tion both of specific LPS and OMP profiles with bovine or ovine diseas e isolates suggested a correlation between specific cell-surface struc tures and host specificity. The combined analysis of capsular serotype s, LPS types and OMP profiles identified seven major groups within P. haemolytica which were responsible for 59 % of the disease cases, sugg esting a clonal structure for this species. Overall, comparison of the capsular serotypes, LPS types and OMP profiles proved extremely usefu l for assessing diversity within P. haemolytica.