HEAT RESISTANCE OF TUBERCLE BACILLI IN LUNGS OF INFECTED MICE

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Abstract
Actively growing and stationary phase cultures of tubercle bacilli were found to differ in their susceptibility to heat at 53[degree]C. This difference was also demonstrable when the cultures were heated in the presence of tuberculous mouse lung. The heat resistance of the infecting bacilli in the lungs of chronically infected mice resembled that of stationary phase cultures. This indicated that the bacilli were in a resting state. This conclusion was supported by the demonstration that the bacilli in the lungs of acutely infected mice were more susceptible to heat, although the difference was small. The constant level of culturable bacilli in the lungs in chronic tuberculous infection in the mouse, therefore, is thought to be due to the persistence of nonmultiplying bacilli rather than to a dynamic equilibrium between multiplication and destruction.