Which M. avium complex (MAC) organism is the most frequently isolated from AIDS patients?

The most frequently isolated organism from AIDS patients within the M. avium complex (MAC) is indeed Mycobacterium avium. This organism is part of a group of non-tuberculous mycobacteria that can cause opportunistic infections in immunocompromised individuals, particularly those with advanced HIV/AIDS.

As immune system function declines in AIDS patients, they become more susceptible to infections caused by organisms that are typically controlled by a healthy immune response. M. avium, in particular, is well-known for its ability to cause disseminated infections in people with CD4 cell counts below 50 cells/mm³. It often presents as a systemic infection, leading to a variety of symptoms and complications.

While M. intracellulare is part of the MAC and can also cause disease, M. avium is the more common cause of MAC disease in this population. Other choices, such as M. scrofulaceum and M. bovis, are not associated with the AIDS patient population to the same extent and do not represent the prevalent infections seen in these individuals. M. scrofulaceum is primarily linked to cervical lymphadenitis in children, and M. bovis is more associated with tuberculosis in humans and livestock