Pneumocystis jiroveci is common in many parts of the world. Particularly in United States, Asia and Europe. The route of organism transmission is believed to be through the transfer of pulmonary droplets by direct person- to- person contact.The population most at risk for Pneumocystis jiroveci is immunosuppressed patients, especially those suffering from AIDS. Children, including malnourished infants and those with predisposing conditions such as a malignancy, have also been traditionally considered a high- risk group.Pneumocystis jiroveci has been known to pass through the placenta and to cause infection in the fetus as well as stillbirth.
Morphology of Pneumocystis jiroveci
Pneumocystis jiroveci, formerly called Pneumocystis carinii, is now considered as a fungus. However, its morphologic and biologic characteristics warrant inclusion in the discussion of miscellaneous protozoan parasites.
The trophozoite or single organism, as it is often referred to, is a simple ovoid and ameboid organism with a single nucleus measuring only 2 to 4 μm.
The cysts of Pneumocystis jiroveci contain four to eight intracystic bodies, also referred to as nuclei or trophozoites in some sources.These nuclei, as they will be called in this text, may be arranged in an organized fashion( in a rosette shape) or unorganized( scattered about the organism). The typical roundish cyst is relatively small and ranges in diameter from 4 to 12 μm.
Life Cycle of Pneumocystis jiroveci
The life cycle of Pneumocystis jiroveci is still considered as unknown. However, it was assumed that once in the host, Pneumocystis jiroveci resides in the alveolar spaces in lung tissue.Rupturing of mature cysts, produces active trophozoites that grow, multiply and feed. The trophozoites finally become pre- cysts and cysts. The cycle would reproduce itself.Sites other than lung have been known to harbor Pneumocystis jiroveci, including the spleen, lung, lymph nodes, and bone marrow
Clinical symptoms of Pneumocystis jiroveci
Pneumocystosis: Atypical Interstitial Plasma Cell Pneumonia
In immunosuppressed adults and children, this condition results in a nonproductive cough, fever, rapid respirations, and cyanosis. These symptoms only occur a few days after onset. Interstitial plasma cell pneumonia is the leading cause of death in patients with AIDS.Interestingly, AIDS persons infected with Pneumocystis jiroveci also often suffer from Kaposi’s sarcoma, a malignant skin disease. Infected malnourished infants suffer from poor feeding, energy loss, rapid respiration and cyanosis. Onset lasts longer, several weeks.
All infected patients typically have a chest x- ray infiltrate. Breathing difficulties may result in a low PO2( arterial oxygen tension) and a normal to low PCO2( carbon dioxide tension). Prognosis is usually poor.The lack of proper exchange of oxygen and carbon dioxide in the lungs is the primary cause of death.
Laboratory Diagnosis of Pneumocystis jiroveci
Although Giemsa and iron hematoxylin stains can be used, the successful diagnosis of Pneumocystis jiroveci is usually done using histological procedures, especially Gomori’s silver nitrate stain methenamine.Serologic techniques have been developed but are not yet considered to be appropriate for clinical diagnosis. Techniques such as monoclonal immunofluorescent stain have also proved helpful in the identification of the organism.Specimens that can be tested for Pneumocystis jiroveci vary and include sputum( usually obtained from immunocompromised individuals), bronchoalveolar lavage, tracheal aspirates, bronchial brushings and lung tissue.
Treatment of Pneumocystis
Trimethoprim- sulfamethoxazole( Bactrim) is regarded by many as the first line of treatment for Pneumocystis jiroveci infections. Alternative treatments include pentamidine isethionate and cotrimoxazole.
Prevention and Control of Pneumocystis
Since some people regard the life cycle of Pneumocystis as uncertain, prevention and control measures are clearly difficult to implement.Based on the assumption that direct person- to- person contact via pulmonary droplets is the route of transmission, personal protection against these droplets is crucial for preventing and controlling the spread of infection.Protective equipment such as a mask worn around known infected persons may be one such measure