Rifamycin S is primarily used in the production of semi-synthetic antibiotics, particularly rifampicin, which is a key drug in the treatment of tuberculosis. It acts by inhibiting bacterial RNA synthesis, making it effective against a range of bacterial infections. Additionally, Rifamycin S is utilized in research to study its mechanism of action and to develop new antimicrobial agents. Its derivatives are also employed in treating other infections, such as leprosy and certain types of meningitis.