What is the recommended prophylaxis against Pneumocystis Jirovecii?

The recommended prophylaxis against Pneumocystis jirovecii, a fungal infection that can lead to severe pneumonia, is trimethoprim-sulfamethoxazole (TMP-SMX). This medication is effective in preventing opportunistic infections in immunocompromised patients, especially those with HIV/AIDS whose CD4 cell counts are below a certain threshold, typically less than 200 cells/mm³.

TMP-SMX works by inhibiting folate synthesis, which is crucial for the growth of many pathogens, including Pneumocystis jirovecii. As a result, it significantly reduces the incidence of Pneumocystis pneumonia (PCP) in at-risk populations.

Other options do not serve as appropriate prophylactic measures against Pneumocystis jirovecii. For example, vancomycin is an antibiotic primarily used to treat Gram-positive bacterial infections and is not effective against fungal pathogens. Acyclovir is an antiviral medication used for infections caused by herpes viruses and has no role in the prevention of PCP. Azithromycin, although effective against certain bacterial infections and used for other preventative measures (such as in patients with chronic lung conditions), is not indicated for Pneumocystis jirovecii prophylaxis.

Therefore,