Snapshot A 28-year-old man presents to the emergency department with worsening shortness of breath and fever. His symptoms began approximately 1 week ago. He has a medical history of HIV infection and he is non-adherent with his antiretroviral therapy. Physical examination is notable for bilateral adventitial sounds. A chest radiograph demonstrates bilateral interstitial infiltrates. His CD4 count is 180/uL. He is started on trimethoprim-sulfamethoxazole. Introduction Mechanism of action login to view 2 more bullets Mechanism of resistance login to view 1 more bullet Clinical use login to view 3 more bullets Adverse reaction login to view 8 more bullets