Treponema spp., the dominant pathogen in the lesion of bovine digital dermatitis and its characterization in dairy cattle.

This study examined the presence of Treponema in lesions using conventional PCR detection methods and investigated the microbiome by performing high-throughput DNA sequencing. Twenty-nine bovine digital dermatitis (BDD) lesions were collected from 25 dairy farms in South Korea that were tested by PCR amplification using sets of one universal, one genus-specific, and three species specific Treponema PCR primers. Three BDD samples were randomly selected and normal tissue samples were submitted for 16S rRNA sequencing using the Illumina MiSeq platform. The dominant phylum present in all tested BDD lesions was Spirochaetes with a mean relative abundance of 46.9 %, and Treponema was the most abundant genus. Spirochaetes abundance was followed by the phyla Tenericutes and Bacteroidetes with 14.1 % and 11.8 % mean abundances, respectively. Co-infecting bacteria from phyla Tenericutes and Bacteroidetes may be involved in the progression of BDD. Bovine digital dermatitis infection is polymicrobial in nature, but Treponema spp. are the main etiologic agents of the disease. In the microbiome results, Treponema pedis had the highest mean relative abundance (20.9 %) in the BDD lesions in this study followed by T. denticola, T. medium, T. lecithinolyricum, Spirochaeta africana, and Sediminispirochaeta bajacalifoniensis. All 29 samples were positive in the genus-specific Treponema PCR results. The species-specific PCR resulted in 75.9 %, 86.2 %, and 69.0 % of samples in groups T. medium/T. vincentii-like, T. phagedenis-like, and T. pedis, respectively. Understanding how these microorganisms mutually interact in the host during certain stages of infection may help in the development of better practices for controlling BDD.