CLONING OF A UNIQUE SEQUENCE-SPECIFIC TO ISOLATES OF TYPE B-2 PASTEURELLA-MULTOCIDA

Two Carter type B Pasteurella multocida isolates, Izatnagar 52 and 25, isolated from cases of haemorrhagic septicaemia (Hs), were used in a modified subtractive hybridisation technique with the specific aim of cloning unique DNA sequences related to the pathogenesis of Hs. Bioche mical and protein analyses have shown these isolates to be similar, bu t reports indicate that they have differences in pathogenicity. The su btracted inserts were screened against genomic DNA from a wide range o f P multocida isolates, with two distinct fragments demonstrating spec ific hybridisation with Carter type B isolates that cause Hs. No ident ity was observed with either Carter type E isolates or non-HS type B s trains. The clones were sequenced and a search of the GenBank database revealed significant identity of the clone A3b (296 nt) to P haemolyt ica lipoprotein, whereas there was no significant identity with 6b (95 6 nt). Both these fragments had a high level of identity (72.8 to 76.9 per cent) to the H influenzae Rd genome.