In vitro susceptibility of bovine digital dermatitis treponemes to conventional and novel antimicrobial agents, and evidence of heavy metal resistance.

We have identified several novel therapeutics with in vitro efficacy against BDD associated treponemes. Moreover, differences in presence of MRGs and in vitro susceptibility across lameness associated bacteria indicate heavy metal tolerance to zinc in BDD treponemes but not in other relevant ruminant lameness associated bacteria, potentially mediated by the tro metal resistance gene. These data appear to explain differences in clinical treatment responses to zinc sulphate observed for different ruminant infectious lameness diseases depending on presence or absence of treponemes and should help inform more tailored treatment approaches in the future.