1.The method designed to test whether or not an apparently amebacidal action is exerted indirectly through inhibition of growth of associated bacteria has been applied to nine antibiotics. It was found that all exhibited some degree of indirect action in vitro.
2.The method has also been used to retest seven accepted amebacides. The slight bacteriostasis observed in two of them (carbarsone oxide and vioform) was insufficient to influence the test. No bacteriostasis was otherwise observed.
3.Indirect action through bacteriostasis has been correlated with oxidation of the culture medium.
4.Direct amebacidal action cannot be determined in the presence of an agent having bacteriostatic activity by the method presented.
Present address: Department of Tropical Medicine and Public Health, Tulane University of Louisiana, School of Medicine, New Orleans, Louisiana.