The specific association of 25 bovine and 6 ovine Histophilus somni strains was observed in the 1465 bp nucleotide residues of the 16S rDNA and the 311 bp region of the rpoB gene. The sequence similarities were 99.4% or more in the 16S rDNA and 98.6 % or more in the rpoB gene. These results suggested that the intra-specific diversities of 16S rDNA and rpoB gene were limited in bovine and ovine strains of H. somni. However, the phylogenetic tree analysis of the rpoB gene showed that the ovine strains appeared to form a subgroup recovered in 70 % of the bootstrap trees. In the 311 bp region of the ovine strains, a Hinc II restriction endonuclease site was detected. The PCR-amplified rpoB DNA of 46 bovine and 20 ovine H. somni strains were examined for the digestion with Hinc II. The results showed that 17 strains of ovine strains were cleaved by the enzyme, but none of the bovine strains appeared to possess the restriction site. The restriction enzyme analysis of rpoB gene may be useful to differentiate ovine strains from bovine strains of H. somni.
(Bacterial Disease Section, Department of Infectious Diseases TEL +81-29-838-7739)
Reference:
Tanaka et al. (2005) J. Vet. Med Sci. 67:255-262.
