Final answer:
The preferred treatment for PCP is oral or intravenous Bactrim, with atovaquone or pentamidine as alternatives. Treatment is necessary upon diagnosis to prevent severe complications and high mortality.
Step-by-step explanation:
The preferred treatment for PCP, or Pneumocystis pneumonia, is with the antimicrobial drug therapy of oral or intravenous Bactrim. In cases where patients cannot tolerate Bactrim, alternative treatments such as atovaquone or pentamidine may be administered. Treatment for PCP is required as soon as the infection is diagnosed, given that if left untreated, PCP can lead to severe complications, including a collapsed lung and near certain mortality. Even with treatment, PCP is a serious condition and contributes to many HIV-related deaths.