Antimicrobial susceptibility of Fusarium, Aspergillus, and other filamentous fungi isolated from keratitis

Objective: To characterize the susceptibility of filamentous fungi isolated from keratitis to amphotericin B, natamycin, caspofungin acetate, itraconazole, voriconazole, and posaconazole. Methods: Ninety isolates from fungal keratitis cases at Aravind Eye Hospital in South India were tested using macrobroth dilution for susceptibility to amphotericin B, natamycin, caspofungin, itraconazole, voriconazole, and posaconazole. The minimum inhibitory concentration ( MIC) median and 90th percentile were determined. Results: The 90 isolates included 41 Aspergillus species, 38 Fusarium species, and 11 others. The triazoles and caspofungin had the lowest MICs against Aspergillus species; voriconazole, amphotericin B, and posaconazole had the lowest MICs against Fusarium species, and none of the Fusarium species were inhibited by itraconazole or caspofungin. Amphotericin B had significantly lower MICs compared with natamycin, but after correcting for the typical prescription dose, natamycin was superior. Conclusion: No single agent was universally most effective, but voriconazole and other triazoles demonstrated the broadest spectrum. Itraconazole and caspofungin were not effective against Fusarium species. Clinical Relevance: Fungal ulcers are commonly treated empirically; drugs are typically selected without regard to susceptibility data. The nonocular infectious disease literature suggests modern fungal susceptibility methods are clinically relevant, but ocular studies are limited. Our results suggest antifungal therapy might be tailored to individual organisms.