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

Intra-specific diversity within Pasteurella trehalosi was investigated by analysis of variation of capsular polysaccharide, and lipopolysacc haride (LPS) and outer-membrane protein (OMP) profiles. Sixty isolates of P. trehalosi, from diverse geographical locations within the UK, w ere examined. Capsular polysaccharide serotypes were determined by ind irect haemagglutination assay; LPS and OMP profiles were compared by S OS-FACE analysis. Capsular serotyping identified three isolates of ser otype T3, 18 isolates each of serotypes T4, T10 and T15, and three unt ypable (UT) isolates. Analysis of LPS and OMP profiles identified six smooth LPS types and four OMP types among the 60 isolates. Forty-five (75%) of the isolates belonged to a single OMP type whereas 52 (87%) o f the isolates possessed one of three LPS types. Each typing method, b y itself, was not very discriminating but when the data from the three methods were combined, the 60 isolates could be separated into 14 dis tinct subgroups containing from one to 16 isolates as follows: serotyp e T3, two subgroups; serotype T4, four subgroups; serotype T10, two su bgroups; serotype T15, five subgroups; UT isolates, one subgroup. Cert ain subgroups were associated with only one serotype whereas other sub groups were common to two or more serotypes. The subgroupings were cap able of differentiating between isolates of the same serotype from the same and different geographical origins. Based on their LPS and OMP p rofiles, isolates of serotypes 14 and T15 were more closely related to each other than to isolates of serotype T10; serotype T4 and T15 isol ates were also more heterogeneous than those of serotype Tin. Certain isolates of serotype T10, recovered from a wide geographical area, wer e characterized by the possession of a unique capsule/LPS/OMP combinat ion and represented a single clonal group which was responsible for a large proportion (31%) of recent disease outbreaks. Overall, a combina tion of capsular serotyping, and LPS and OMP typing, was found to be e xtremely useful for assessing diversity within P. trehalosi and should be of value for epidemiological and virulence studies.