Multi-drug resistant TB is due to acquired drug resistance due to persistence. It has been 30 years since the introduction of a new TB drug. HIV epidemic is feeding TB epidemic. Emerging infections take precedence in research funding and development. 2x week, Isoniazid, Rifampin Toxicities are high.
Patient compliance is a major problem.
But, how bacteria causes disease is not known. It is known, for example, that with cholera, the bacteria make toxins and the toxins cause disease. One theory of how TB causes disease is that the body's chronic response to TB is what causes disease. Host immune response can be damaging to host cells. Gradual damage is due to chronic conditions.