The guinea pig has recently proven to be a useful and realistic animal model in which to test new drug regimens for their potential to treat disease caused by Mycobacterium tuberculosis. We previously showed that two regimens reduced the bacterial load in this model to non-culturable levels, but about a year thereafter a significant portion of these animals underwent spontaneous disease reactivation. In the present report we show the results of a small study in which we took healthy remaining animals and attempted to induce disease reactivation using cortisone. Ten guinea pigs that had remained completely healthy 11-months after drug therapy were treated in this manner, and a month later two of the animals, which had originally received a “fast-acting” regimen of rifampacin, pyrazinamide, and the experimental drug TMC207, showed severe reactivation, with large numbers of bacilli culturable from the lungs and other organs. Despite this, while acid fast bacilli could be detected, their staining was unusually weak. Thus, while new drug regimens are being developed for tuberculosis that seems to be fast acting, our data suggests this does not absolutely guarantee organ sterility. In addition, the poor acid fastness observed in reactivating animals might be explained in the context of new information regarding the physiology of these persisting organisms.
Shaobin Shang, C. A. S., & Randall J Basaraba, M. L. C. (2013). Cortisone-Forced Reactivation of Weakly Acid Fast Positive Mycobacterium Tuberculosis in Guinea Pigs Previously Treated With Chemotherapy. Mycobacterial Diseases, 02(04). https://doi.org/10.4172/2161-1068.1000116