In drawing conclusions from the in vivo models during experimental processes, Wayne (1994) indicated that there was a capacity for prolonged periods (even decades) of dormant or latency, inactivity of Mycobacterium tuberculosis and this accounted for increasing development of active tuberculosis in elderly individuals. This was concluded to be associated with age-related decline in the individual’s immune response system. (p. 909). Dick, T. & the British Society for Antimicrobial Chemotherapy. “Dormant tubercule bacilli: the key to more effective TB chemotherapy”. Oxford Journal of Antibacterial Chemotherapy.
(2001). Retrieved from http: //jac. oxfordjournals. org/content/47/1/117/ [Web]. In the research-based article, “Dormant tubercule bacilli: the key to more effective TB chemotherapy” by T. Dick (2001), the key research question explored states, “…the problem in tuberculosis control is the persistence of Mycobacterium tuberculosis despite prolonged chemotherapy” (p. 117). As demonstrated during in vivo specimen and culture analysis, “treatment for six to twelve months is required to cure acute disease or eliminate latent or dormant infection. The research question: Why does it take so long to eradicate the bacilli once they reside within the human host”?
(Dick, 2001, p. 117). The answer, Dick proposed, could lie in the development of physiological (as opposed to genetic) drug resistance. According to research conducted within Dick’s Mycobacterium laboratory, supported by the Institute of Molecular and Cell Biology (IMCB), the link between the Mycobacterium being categorized as an obligate aerobe – a bacterium that can live only in the presence of oxygen (O2) -- drug resistance and latency was a focus of in vitro research studies.
Via laboratory studies, it was established that “there was a link between starvation for oxygen and drug resistance (Wayne & Hayes, 1996). During in vitro analysis, it was demonstrated that depletion of oxygen experimental culture, Mycobacterium tuberculosis terminates growth and develops latency, a defined non-replicating dormant form. The dormant, latent form of the bacilli is anaerobic and can remain dormant for extended periods of time. Scientifically speaking, “…the bacilli is arrested at a uniform stage of the cell cycle and and play a significant role in in vivo cultures” (Dick& Wayne, 1996, p.
117). It was in observing and analyzing both the in vitro and in vivo laboratory findings together that the working model, often used to explain activities of genetically drug-sensitive bacilli during chemotherapy, can be proposed.