Rapid detection of lytic antimicrobial activity against yeast and filamentous fungi.

A rapid method for assessing the lytic activity of antimicrobial agents against yeast and fungi has been developed. The assay is based on the release of the intracellular enzyme, maltase (alpha-glucosidase). The released maltase activity was measured colorimetrically by the production of p-nitrophenol from p-nitrophenyl-alpha-D-glucopyranoside (PNPG). The lytic activity of different antimicrobial compounds was measured against yeast cells or germinating spores of filamentous fungi. Lytic anti-yeast activity could be detected within 20 min incubation at 30 degrees C against Saccharomyces cerevisiae, Candida albicans, and Cryptococcus neoformans. Lytic anti-fungal activity appeared after 2 h of incubation at 30 degrees C against germinating spores of Aspergillus niger and Botrytis cinerea. Whole cells of either yeast or fungi did not hydrolyze sufficient PNPG within 3 h at 30 degrees C to yield a detectable color change. Lytic activity of enzymes (e.g., Lyticase), antibiotics (e.g., Amphotericin B), and an antibiotic-producing strain of bacteria were detected using the assay. The anti-yeast assay has been adapted to a 96-well microtiter format. Both assays provided a rapid, sensitive, and reproducible detection of lytic anti-yeast and anti-fungal activity.