Phylogenetic Studies on Corynebacterium bovis Isolated from Bovine Mammary Glands

Coryneform bacteria are frequently isolated from bovine mastitis with the lipophilic species, and Corynebacterium bovis is the most frequently isolated organism of this group. However, previous studies on the phylogeny of corynebacteria have incorporated only a single reference strain. We examined the phylogeny of C. bovis using 47 strains isolated from bovine mammary glands. Phylogenetic studies were performed by direct sequencing of the 16S ribosomal RNA and comparison to sequences of reference strains. All strains identified as C. bovis demonstrated similarity of 98% or higher to the ribosomal RNA gene sequences of the type strain of C. bovis. Phylogenetic analyses indicated that all strains tested clustered with members of the Corynebacterium urealyticum group confirming that C. bovis is a legitmate member of the genus Corynebacterium. Further investigation into the diversity within the species using repetitive element palindrome PCR indicated only minor differences between the strains tested. Corynebacterium bovis ATCC 13722 demonstrated the highest similarity (95%) with Brevibacterium helvolum, indicating that this organism does not belong in the genus Corynebacterium.