A zoospore inhibition technique to evaluate the activity of antifungal compounds against Batrachochytrium dendrobatidis and unsuccessful treatment of experimentally infected green tree frogs (Litoria caerulea) by fluconazole and benzalkonium chloride

Effective and safe treatments of chytridiomycosis in amphibians, caused by Batrachochytrium dendrobatidis, are needed to help prevent mortality in captive programs for threatened species, to reduce the risk of spread, and to better manage the disease in threatened populations. We describe a simple method to determine minimum inhibitory concentrations (MICs) of antifungal agents that involves adding zoospores to various drug concentrations in 96 well plates and microscopic observation after four days. We report results from testing 10 commercially available antifungal compounds: benzalkonium chloride (<0.78 μg/ml), povidone iodine (312.5 μg/ml), amphotericin B (3.125 μg/ml), fluconazole (<1.56 μg/ml), itraconazole (<1.56 μg/ml), enilconazole (<1.56 μg/ml), mercurochrome (6.25 μg/ml), sodium chloride (12.5 mg/ml), methylene blue (