Pneumocystis carinii

“Sometimes our understanding of something is limited by our technology.”

Case in point? The original description of Pneumocystis carinii placed it in Apicomplexa, as a relative of Toxoplasma. Its current taxonomic status?: From: J Clin Microbiol. 2001 Jun;39(6):2126-33. Phylogeny of Pneumocystis carinii from 18 primate species confirms host specificity and suggests coevolution. Demanche C, Berthelemy M, Petit T, Polack B, Wakefield AE, Dei-Cas E, Guillot J. UMR 956 INRA-AFSSA-ENVA Biologie Moléculaire et Immunologie Parasitaires et Fongiques, Ecole Nationale Vétérinaire d'Alfort, 7, Avenue du Général de Gaulle, 94704 Maisons-Alfort, France. Primates are regularly infected by fungal organisms identified as Pneumocystis carinii. They constitute a valuable population for the confirmation of P. carinii host specificity. In this study, the presence of P. carinii was assessed by direct examination and nested PCR at mitochondrial large subunit (mtLSU) rRNA and dihydropteroate synthetase (DHPS) genes in 98 lung tissue samples from captive or wild nonhuman primates. Fifty-nine air samples corresponding to the environment of different primate species in zoological parks were also examined. Cystic forms of P. carinii were detected in smears from 7 lung tissue samples corresponding to 5 New World primate species. Amplifications at the mtLSU rRNA gene were positive for 29 lung tissue samples representing 18 different primate species or subspecies and 2 air samples corresponding to the environment of two simian colonies. Amplifications at the DHPS gene were positive for 8 lung tissue samples representing 6 different primate species. Direct sequencing of nested PCR products demonstrated that a specific mtLSU rRNA and DHPS sequence could be attributed to each primate species or subspecies. No nonhuman primate harbored the human type of P. carinii (P. carinii f. sp. hominis). Genetic divergence in primate-derived P. carinii organisms varied in terms of the phylogenetic divergence existing among the corresponding host species, suggesting coevolution. PMID: 11376046 [PubMed - indexed for MEDLINE]

Pneumocystis carinii

Images: Pneumocystis cysts in rat “noseprint” – slide treated with “ether-sulfuric”, a mixture of ether and sulfuric acid, and then stained with Toluidine Blue.

Phylogeny:
Uncertain (Ribosomal RNA analysis suggests affinity to Fungi)

Preferred definitive host:
Apparently none. It is a saprophyte found in the lungs of many species of animals.

Reservoir hosts:
None

Vector/intermediate host:
None

Geographical location:
Cosmopolitan

Organs affected:
Lungs

Symptoms and clinical signs:
This organism causes interstitial pneumonia among immunosuppressed individuals. Among children, it may cause sever dyspnea, tachypnea, cyanosis, and instant death. Among adults, it may cause a dry, hacking cough, cyanosis, and dyspnea. Mild cases may show minimal alveolar septal infiltration with lymphocytes and occasional plasma cells, but sever cases may show widespread interstitial and alveolar edema,. with lymphocytic and plasma cell infiltration, necrosis of alveolar walls, and masses of P. carinii in the alveoli.

Treatment:
Pentamidine isethionate, Trimethroprim and sulfamethoxazole.