Determination of antimicrobial activity of plant-derived polyphenols against Malassezia pachydermatis and Staphylococcus intermedius

: The emergence of antimicrobial-resistant pathogens has significantly affected treatment outcomes for malasseziosis and pyoderma in dogs. Here, we determined the antimicrobial activity of plant-derived polyphenols against Malassezia pachydermatis and S. intermedius , the causative agents of malasseziosis and SIG infection, respectively. The polyphenols tested were castalagin, (+)catechin, ( − )-epigallocatechin, ( − )-epicatechin gallate, ( − )-epigallocatechin-3-O-gallate, myricitrin, prodelphinidin, procyanidin, resveratrol, rutin, theaflavin, and thearubigin. Minimum inhibitory concentration (MIC) values of these polyphenols against two yeast species, M. pachydermatis and Candida albicans , and two bacterial species, S. intermedius and Achromobacter xylosoxidans , were determined using an agar plate assay. Castalagin had the lowest MIC values against M. pachydermatis (100 μg/ml) and S. intermedius (50 μg/ml), suggesting its therapeutic potential for skin diseases caused by these microbes in dogs.