In vitro susceptibility to antimycotics of Microsporum canis isolates from cats

One hundred thirty-four isolates of Microsporum canis, obtained from cats, were tested for in vitro susceptibility to various antifungal agents. The fungi were classified as susceptible, resistant, and intermediate by measuring the size of the zone of inhibited growth on yeast nitrogen base agar medium. Clotrimazole had the highest activity (99.2%), followed by tioconazole (89.6%), griseofulvin (88.8%), econazole (73.1%), ketoconazole (50.7%), miconazole (15.7%), and isoconazole (12.7%). We found 14.9% of the isolates to be susceptible to all the assayed drugs, whereas the highest resistance frequency (41.8%) was against 2 antimycotics. A simultaneous resistance to all the tested antimycotics was not found. The differences among the antifungal drugs activity were examined, and administration of drugs for which a simultaneous resistance was minimal is suggested.