An <i>in vitro</i> method for testing synergistic action of parasiticides using malachite green and formalin as a model system

Abstract

Abstract. An in vitro technique was developed to screen drugs for toxicity to laboratory cultured protozoans. Drugs were diluted using standard microtitration equipment. An easily cultured protozoan, Tetrahymena pyriformis , was added to the dilutions of drugs and viability was checked daily for 10 days. Drugs used as a model system to test the technique were formalin and malachite green. Effective concentrations of formalin determined by this in vitro technique were close to recommended therapeutic treatment levels for Ichthyophthirius . Malachite green was effective at concentrations in excess of recommended therapeutic treatment levels for Ichthyophthirius . The synergistic effect of formalin and malachite green was demonstrated. This technique can he of use in determining effectiveness of new drugs as parasiticides.