The human body is infected with Mycobacterium tuberculosis, and those who are positive for tuberculin skin test become infected. About 10% of these people develop tuberculosis and become infected; the rest of the infected people can have tuberculosis bacilli latent in their bodies for a long time, waiting for an opportunity to “rekindle” and develop the disease. This is the latent nature of Mycobacterium tuberculosis in the body. Persistence In a large population of Mycobacterium tuberculosis (for example, a single cavity can contain more than 100 million Mycobacterium tuberculosis bacteria), most of the bacteria are fast-growing. In general, they are sensitive to anti-tuberculosis drugs, such as isoniazid, rifampin, streptomycin, etc., and are easily killed, so many TB patients often have significant improvement or even disappearance of symptoms and significant reduction or even momentary negative sputum count of Mycobacterium tuberculosis after short-term regular treatment. However, there are some slow metabolizing or intermittent metabolizing bacilli, which can be latent in macrophages or closed case-like lesions for a long time, and we call them persistent bacilli. These persistent bacteria are the main source of recurrence and deterioration of tuberculosis. Therefore, it is necessary to use drugs that are effective in killing the persistent bacilli for a longer period of time in order to achieve a complete cure and to reduce and prevent recurrence. Drug resistance There are very few naturally drug-resistant bacteria in the tuberculosis flora that are resistant to various anti-tuberculosis drugs. Therefore, after using single drugs to kill a large number of drug-sensitive bacteria, a small number of naturally drug-resistant flora – drug-resistant Mycobacterium tuberculosis – will evolve into the dominant flora. Therefore, the treatment of tuberculosis requires a combination of drugs, including drugs with bactericidal and sterilizing activities that have advantages for fast-growing, slow-growing, and intermittent-growing bacilli, so as to play a synergistic or additive role between drugs and kill the bacilli in an all-round way to greatly improve the cure rate, minimize recurrence, and prevent patients from developing drug resistance.