Papillomatous digital dermatitis (PDD) is a
foot disease causing lameness in dairy cattle. It is regarded as a
polymicrobial infection, although its etiology is not fully understood. PDD is treated by the topical or systemic administration of
antibiotics such as
lincomycin (LCM); however, the milk of the cows cannot be marketed during the treatment and withdrawal period due to the residual
antibiotics in milk.
Allyl isothiocyanate (
AITC), an extract of Wasabia japonica (known as wasabi or Japanese horseradish) widely employed as a
food additive, can be used as an alternative
antimicrobial agent that overcomes this problem. We previously showed that
AITC is as effective as LCM in PDD treatment. Here, using the samples obtained in the previous clinical study, we analyzed changes in the bacterial population in the PDD-associated microbiota after
AITC treatment and compared those with that following LCM treatment by
16S ribosomal RNA (rRNA)-based amplicon analysis. Both treatments induced major changes in the bacterial population, and Treponema species, which have been regarded as the major causative agents of PDD, were efficiently eliminated by both agents. However, the
AITC-treated samples exhibited higher diversity compared with pretreatment samples, but this trend was not observed for LCM treatment, probably reflecting different antibacterial activities of the two agents. Importantly, this analysis detected population changes before morphological changes in PDD lesions (clinical signs of healing) became evident, indicating that
16S rRNA-based amplicon analysis represents an efficient strategy for analyzing and monitoring the treatment efficiency of PDD as well as other polymicrobial diseases.