E F F E C T of T H E Composition of T H E Gaseous and Aqueous Environments on T H E Survival of Tubercle Bacilli I N Vitro by Reni~ J. Dubos, I~.d

One of the mechanisms which has been invoked to account for the progressive disappearance of tubercle bacilli from certain types of tuberculous lesions (closed cavities, cold abcesses, etc.) is the low oxygen tension prevailing in these areas. As far as is known, tubercle bacilli depend upon molecular oxygen for growth, and the rate and extent of their multiplication decredse rapidly in proportion as the oxygen tension falls below that of ordinary air (1-4). I t appears, moreover, that anaerobic conditions are unfavorable to the maintenance of their viability, and metabolic activity (5, 6). Low oxygen tension is, of course, only one of the characteristics of the closed tuberculous lesion which renders its physicochemical environment different from that prevailing in the rest of the body. Among other differences which can be surmised to be of importance for the multiplication and survival of tubercle bacilli, are the concentration of C02 in the aqueous and the gaseous phases and the presence of organic acids produced by anaerobic metabolism and of other unusual substances released from the tissues by autolytic processes. The experiments to be described in the present paper were designed to test the effect on the viability of tubercle bacilli of some of the factors presumed to be present and to operate in the tuberculous lesion.