In vitro studies with ambruticin, a new antifungal antibiotic.

The in vitro antifungal inhibitory activities of ambruticin and of various antifungal drugs of choice against 190 fungal pathogens representative of the major human mycoses were compared using a modification of the ICS agar dilution technique. Ambruticin compared favorably with amphotericin B and miconazole when tested against the dimorphic pathogens Coccidioides immitis, Histoplasma capsulatum, and Blastomyces dermatitidis and against Aspergillus fumigatus. Miconazole was the most active compound against Sporothrix schenckii, Allescheria (Petriellidium) boydii, and selected dematiaceous fungi, with ambruticin giving minimal inhibitory, concentrations from 3- to 74-fold higher. Ambruticin compared unfavorably with amphotericin B and 5-fluorocytosine when tested against Candida and Torulopsis species. Ambruticin was not as active in vitro as tolnaftate when tested against the three genera of dermatophytic fungi, but compared favorably with miconazole.