Final answer:
Pneumocystis jiroveci pneumonia (PCP) prophylaxis should be initiated in HIV-positive patients with a CD4 count less than 200 cells/μL. Mycobacterium avium-intracellulare (MAI) prophylaxis is recommended for HIV-positive patients with a CD4 count less than 50 cells/μL.
Step-by-step explanation:
Pneumocystis jiroveci pneumonia (PCP) prophylaxis should be initiated in HIV-positive patients when their CD4 count is less than 200 cells/μL or when they have a history of a prior episode of PCP. PCP is caused by the fungus Pneumocystis jirovecii and is commonly found in patients with AIDS and other immunocompromised individuals.
On the other hand, Mycobacterium avium-intracellulare (MAI) prophylaxis is recommended for HIV-positive patients with a CD4 count less than 50 cells/μL. MAI is a bacterial infection that can cause severe disease in immunocompromised individuals.