A guinea pig model of experimental airborne tuberculosis for evaluation of the response to chemotherapy: the effect on bacilli in the initial phase of treatment

The purpose of this study was to develop and evaluate a guinea pig model of experimental airborne tuberculosis for its ability to assess chemotherapeutic regimens for their efficacy against virulent tubercle bacilli in vivo during the initial phase of treatment. The tissues examined included primary lung lesions and the metastatic foci in lung and spleen which result from the naturally occurring bacillaemia. The treatments examined, INH+RIF, INH+EMB, EMB+RIF, were initiated 4 weeks after infection and were continued for 8 weeks. Although minor differences were observed in the time of onset of a significant bactericidal effect or in the rate of decline in the microbial population, all three treatment combinations resulted in a significant reduction in the number of M. tuberculosis H37Rv recovered from primary lung lesions, primary lesion-free lung lobes and spleen. X-rays taken of excised inflated lung lobes showed a relationship between the degree of calcification of primary lung lesions and the number of surviving bacilli.