clarithromycin + ethambutol + rifabutin

A three-drug oral antibiotic combination of **clarithromycin** (a macrolide antibiotic), **ethambutol** (an antimycobacterial agent), and **rifabutin** (a rifamycin antibiotic), primarily used for the treatment of *Mycobacterium avium* complex (MAC) infections, especially in immunocompromised patients such as those with AIDS. This regimen acts synergistically to inhibit different aspects of mycobacterial physiology: clarithromycin inhibits bacterial protein synthesis by binding the 50S ribosomal subunit; ethambutol interferes with mycobacterial cell wall formation by inhibiting arabinosyl transferases; and rifabutin suppresses DNA-dependent RNA polymerase, thereby inhibiting RNA synthesis. This combination is standardly recommended by the American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA) for MAC and is a mainstay in multidrug therapy to prevent resistance and achieve effective long-term suppression or cure of infection.