Abstract
Resistances of tubercle bacilli occurring in patients to alpha-ethyl-thioisonicotinamide (1314 Th) and thiosemicarbazone were determined by a direct method of the drug resistance test.
Natural resistance to 1314Th was not always accompanied by thiosemicarbazone resistance and there was only a random relationship between natural 1314Th resistance and thiosemicarbazone resistance. On the other hand, acquired resist ance to 1314Th was mostly accompanied by an increase of thiosemicarbazone resistance, although the latter drug was never administered. Thus, there exists an in vivo one-way cross resistance relationship between 1314Th and thio semicarbazone.
Natural resistance to 1314Th was thought to differ from the acquired resistance to 1314Th in the origin and nature of resistance.
