Studies on Methods for Evaluation of Anticoccidial Drugs in Vitro

Abstract

Experiments were made to determine whether a cell culture method wouldbe suited for evaluating anticoccidial drugs in vitro. Eleven anticoccidial drugs with ananticoccidial effect proved in vivo were used. They were five thiamine antagonists, twoquinoJones, one pyridone, one sulfonamide and two antibiotics. Chick embryo and kidneycell cultures were prepared for each experiment. It was proved that all the drugs exertedanticoccidial activities in vitro, as they did in vivo. The optical conditions for the activi-ties varied with the type of drug.The effects of antibiotics could be evaluated in terms of inhibition of the penetration ofsporozoites into the cultured cells. The effects of the quinolones and pyridone could beassessed in terms of inhibition of the development of schizonts beyond the intracellularsporozoites. It was necessary to administer the thiamine antagonists and sulfonamide con-tinually after inoculation with sporozoites. A quinolone-resistant strain of Eimeria tenellawas not affected by the quinolones in a concentration in which these drugs had been provedactive on susceptible strains.