A team of Indian researchers has been able to achieve 100-fold reduction in TB bacterial load in lungs of mice after 60 days of treatment using bergenin — a phytochemical isolated from tender leaves of sakhua or shala tree (Shorea robusta). Unlike the regularly used antibiotic drugs that target the TB bacteria, the bergenin compound modulates the immune system to kill the bacteria found inside the macrophages (a type of white blood cells). The results were published in the journal Frontiers in Cellular and Infection Microbiology.The researchers undertook several studies to understand the mode of action of the compound. The compound was unable to directly kill TB bacteria when treated with the compound. However, in the case of in vitro studies, the compound was able to kill the bacteria found inside infected cells. In mice infected with TB and treated with the compound, there was significant reduction in the bacterial load in the lungs. Unlike in the case of in vitro studies The bergenin compound was selectively enhancing the frequency of interferon-gamma and interleukin-17-producing T cells in the TB infected animals. Interferon-gamma promotes bacteria-killing nitric oxide inside macrophages thus promoting the generation of protective immune responses against TB bacteria.The compound can be used in patients with drug-resistant TB too, as it does not target the bacteria directly but modulates the immune system to kill the bacteria.