Comparative Genomics of , an Undescribed Bacterium Isolated from Dairy Mastitis.

This study characterizes 81 isolates from bovine mastitis (of which 80 were subclinical). The isolates were first identified as by MALDI-TOF MS, but later whole genome sequencing analysis allowed reclassification as The isolates were derived from 52 cows and nine dairy herds in Denmark. To describe the pathogenicity of , we used whole genome sequencing to infer the distribution of genes associated with virulence, antibiotic resistance, and mobile genetic elements. Also, we performed a core-genome phylogeny analysis to study the genetic relatedness among the isolates. All 81 isolates expressed the same virulence profile comprising two putative virulence genes, and . Three isolates carried a resistance gene encoding streptomycin () or lincomycin () resistance. The distribution of plasmids suggested the detected antibiotic resistance genes to be plasmid-mediated. Phages were abundant among the isolates, and the single isolate from clinical mastitis acquired a phage disparate from the rest, which potentially could be involved with virulence in . The core genome phylogeny revealed a strong genetic intra-herd conservation, which indicates the source of introduction being herd-specific and might further imply the ability of to adapt to the bovine niche and spread from cow-to-cow in a contagious manner. With this study, we aim to acquaint clinicians and professionals with the existence of which might have been overlooked so far.