The type 4 fimbrial subunit gene of pasteurella multocida

Colonisation of host tissue by Gram- negative bacteria is facilitated by various adhesins, one of which is type 4 fimbriae (pili). These structures have been associated with pathogenesis in several bacterial species, and have been shown to mediate colonisation of epithelial surfaces. Recently, type 4 fimbriae were identified and characterised from P. multocida strains A, B and D. The type 4 fimbrial subunit protein (PtfA) was identified as an 18-kDa protein which was isolated from whole membrane fractions. We report here the isolation and characterisation of the gene (ptfA) encoding the PtfA protein from P. multocida VP161 (serotype A:1). Part of the gene was cloned on a 2-kb genomic DNA fragment. The complete ptfA gene was obtained using inverse PCR. The gene and its flanking regions were characterised, and the deduced PtfA amino acid sequence was compared to type 4 subunit protein sequences from other bacterial species. The ptfA gene was amplified and sequenced from several P. multocida strains. Comparison of these sequences revealed variation within the type 4 subunit gene of P. multocida.