In vitro antifungal activity of gentian violet.

Gentian violet, a compound that gained wide acceptance in the poultry industry as a mold inhibitor in feed, was tested for its activity against eight aflatoxigenic strains of Aspergillus flavus and A. Parasiticus. In a simple nutrient medium, it completely inhibited growth of all strains at 8 micrograms/ml. When chicken feed was added to the medium, the inhibition by the same concentration ranged from 12 to 44% depending on the strain. Observations suggested that both the feed and the fungi were involved in the resistance conferred by chicken feed. Growth and aflatoxin production on moist rice was inhibited in one strain but not in a second strain. Inoculating autoclaved chicken feed of varying moisture contents with pure cultures revealed that the activity of gentian violet was better at high moisture contents than at low moisture contents approximating those found in poultry feed. It was not possible to assess the activity of gentian violet in unaltered chicken feed. Attempts failed because the formation of reproducible levels of aflatoxin could not be attained.