Corynebacterium mastitidis sp. nov., isolated from milk of sheep with subclinical mastitis.

Fourteen strains of a hitherto unknown catalase-positive, aerobic, gram-positive coryneformlike organism were isolated from the milk of sheep with subclinical mastitis from different regions of Spain. The strains phenotypically closely resembled one another and biochemically were similar to Corynebacterium urealyticum and Corynebacterium afermentans subsp. lipophilum. The results of chemotaxonomic investigations were consistent with membership in the genus Corynebacterium, and comparative 16S rRNA gene sequencing studies showed that the unknown bacterium from sheep was indeed a member of the genus Corynebacterium. Within the genus Corynebacterium the new bacterium formed a distinct subline that exhibited > 4% sequence divergence with other species. Based on both phenotypic and phylogenetic findings, a new species, Corynebacterium mastitidis, is proposed for the organisms from mastitic sheep. The type strain of C. mastitidis is CECT 4843 (= S-8).