American Board of Internal Medicine (ABIM) Certification Practice Exam

Which is a typical treatment regimen for Mycobacterium avium complex infection?

1. Vancomycin and azithromycin

2. Amoxicillin and clavulanic acid

3. Clarithromycin and ethambutol

4. Ciprofloxacin and metronidazole

The correct answer is: Clarithromycin and ethambutol

The typical treatment regimen for Mycobacterium avium complex (MAC) infection primarily involves the use of clarithromycin and ethambutol. This combination is effective because clarithromycin, a macrolide antibiotic, specifically targets the mycobacterial cell wall and inhibits protein synthesis, making it effective against the slow-growing bacteria of the MAC. Ethambutol complements this by inhibiting arabinogalactan synthesis in the cell wall of mycobacteria, which further aids in reducing microbial replication and enhancing efficacy. This treatment is aimed at addressing the unique characteristics of MAC, which is associated with opportunistic infections commonly seen in immunocompromised patients, particularly those with HIV/AIDS. Using clarithromycin helps to achieve effective plasma concentrations necessary for the treatment of this type of infection due to the organism’s particular growth rate and location within the body’s tissues. The other options do not target the MAC effectively. For example, vancomycin and azithromycin, while effective for staphylococcal infections, are not appropriate for treating MAC. Likewise, amoxicillin and clavulanic acid are primarily effective against enterobacteriaceae and are not suitable for mycobacterial infections. Ciprofloxacin and metron