In vitro susceptibility studies with oxiconazole (Ro 13-8996)

Oxiconazole (Ro 13-8996) is a recently described imidazole derivative intended for topical use. 128 isolates of pathogenic fungi were tested in vitro against oxiconazole, miconazole, and ketoconazole using an agar dilution method. Results indicated that miconazole was markedly more active than either oxiconazole or ketoconazole against Candida albicans while ketoconazole was the more active compound against Candida parapsilosis. A species specific difference in the susceptibilities of isolates of Aspergillus fumigatus and Aspergillus flavus to all three imidazoles with A. flavus being more susceptible was noted. Both Mucor and Rhizopus were more susceptible to oxiconazole than to either miconazole or ketoconazole. There were no noticeable differences among the dermatophytes in tests with the three drugs with all geometric mean minimum inhibition concentrations (MIC) being less than 1.0 micromilligram-1. The dematiaceous fungi also demonstrated no major differences in susceptibility to the three drugs. One isolate of Pseudallescheria boydii was relatively resistant to all three drugs (MIC greater than or equal to 16 micromilligrams-1).