Pneumocystis jiroveci is a fungus. (Jiroveci is pronounced "yee row vet zee"). This parasitic organism was earlier classified as a protozoan, and still is sometimes called by its former name Pneumocystis carinii. It causes the disease pneumocystis pneumonia (PCP), which afflicts people with weakened immune systems, such as children, the elderly, and especially AIDS patients, in whom it is most commonly observed today. It was first recognized in institutional epidemics among malnourished children and infants. The actual life cycle is unknown. Debate continues as to whether or not the parasite is transmitted through latent infection or active infection. Historically it was thought to be latent, with a duration of up to a year, but recent studies suggest an active state. Symptoms of infection include shortness of breath, nonproductive cough, and low grade fever. Death by asphyxia is a consequent threat, as in any pneumonia. Diagnosis is best done through bronchial biopsy but most commonly performed in bronchoalveolar washes or sputum. Antibiotic treatment is available; supportive treatment includes supplementary oxygen.

Pneumocystis infection is diagnosed by immunofluorescent or histochemical staining of the specimen.

In immunocompromised patients (e.g., cancer patients on chemotherapy, or AIDS patients with a CD4+ T-cell count below 200/μl), prophylaxis with regular pentamidine inhalations or sulfamethoxazole/trimethoprim (co-trimoxazole or TMP-SMX) may be necessary to prevent PCP.

The organism is distributed worldwide.

Nomenclature

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The name P. jiroveci, to distinguish the organism found in humans from other variants of Pneumocystis, was first proposed in 1976 in honor of Otto Jirovec, who originally described Pneumocystis pneumonia in humans in 1952. After DNA analysis showed significant differences in the human variant, the proposal was made again in 1999 and has come into common use; P. carinii still describes the species found in rats, while P. murina describes that found in mice. The International Code of Botanical Nomenclature would normally require the name to be spelled jirovecii rather than jiroveci; both spellings are currently in use.

References

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• A New Name (Pneumocystis jiroveci) for Pneumocystis from Humans - from the Centers for Disease Control.
• Dr. Micheal Kent "Microsporidia". Microbiology 480. Oregon State University. Weigand 115, May 24th 2006.

Ascomycetes | Pneumocystose | Pneumocystis jiroveci | Pneumocistose