Antimicrobial action of compound 48/80 against protozoa, bacteria, and fungi.

Compound 48/80 inhibited the growth of protozoa, bacteria, and fungi but had no effect on the multiplication of viruses. All susceptible organisms were inhibited by 10 microgram/ml of crude compound 48/80, and some were inhibited by as little as 0.1 microgram/ml. Against Tetrahymena pyriformis, this drug was seven times more potent than quinine. Separation of compound 48/80 into different fractions indicated that some antimicrobial activity could be separated from the histamine-liberating activity. It was found that compound 48/80 is not surface active at 500 microgram/ml.