PCP is extremely rare in healthy people. Most people who get PCP have weakened immune systems due to HIV/AIDS, cancer treatments, or organ transplants. Other groups of people who are at risk for PCP include:

HIV-exposed but uninfected children
People who are receiving immunosuppressive therapies, such as organ transplant patients
People with connective tissue diseases or chronic lung diseases

How can I prevent pneumocystis pneumonia (PCP)?

There is no vaccine to prevent PCP. Some groups of people who are at high risk of developing PCP may need to take a medication called TMP-SMX to prevent the illness from occurring. If your doctor thinks you are at risk for developing PCP, he or she might prescribe this medicine for you. TMP-SMX prophylaxis is currently recommended for:

All HIV-infected patients with CD4 < 350 cells / µL
Infants born to HIV-infected mothers
Children with a history of PCP
Stem cell transplant patients

CDC - People at Risk for Pneumocystis pneumonia

CDC - Diagnosis & Testing of Pneumocystis pneumonia

Pneumocystis pneumonia Diagnosis and Testing

P. jirovecii cysts in a smear of bronchoalveolar lavage material.

PCP is diagnosed by using a microscope to identify P. jirovecii organisms in a sample of lung fluid or tissue. The sample is usually induced sputum or bronchoalveolar lavage (BAL) material. It may be necessary to get the sample through transbronchial biopsy or open-lung biopsy – these diagnostic techniques are more sensitive and specific, but they are also more invasive.
Polymerase chain reaction (PCR) is also used to detect P. jirovecii DNA in clinical specimens. PCR can be particularly helpful in detecting silent P. jirovecii infections in HIV-infected patients.

Treatment and Outcomes for Pneumocystis pneumonia

PCP requires treatment with prescription medicine that must be taken for three weeks. The best form of treatment for PCP is trimethoprim sulfamethoxazole (TMP-SMX), which is also known by the brand names Bactrim, Septra, and Cotrim. This medicine is given orally or through a vein.
TMP-SMX can cause negative side effects such as a rash and nausea, but the benefits of treating the PCP usually outweigh the risks of these side effects. Without treatment, PCP can be fatal.

CDC -Treatment & Outcomes of Pneumocystis pneumonia