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Pneumocystis carinii: an update

Gurdip S Sidhu1, Nicholas D Cassai, Zhiheng Pei

  • 1Department of Pathology, New York University School of Medicine, New York, New York, USA. deepsidhu@aol.com

Ultrastructural Pathology
|May 15, 2003
PubMed

Insights

Pneumocystis, a fungus causing respiratory infections in immunocompromised individuals, is now classified as an Archiascomycetous fungus. Research suggests adult infections are new, not latent, impacting prevention strategies.

Area of Science:

  • Medical Mycology
  • Infectious Diseases
  • Molecular Taxonomy

Background:

  • Pneumocystis causes respiratory infections in immunocompromised mammals, with species specific to each host.
  • The human-infecting species, formerly P. carinii, is now P. jirovecii.
  • Pneumocystis was long considered a protozoan parasite.

Purpose of the Study:

  • To re-evaluate the classification of Pneumocystis.
  • To investigate the infectious nature of Pneumocystis in adults.

Main Methods:

  • DNA sequence analysis of ribosomal RNA (srRNA) genes.
  • Morphological examination, including nucleus-associated organelles.
  • Ultrastructural analysis for evidence of sexual reproduction.

Main Results:

  • Molecular data suggests Pneumocystis belongs to the Archiascomycetous fungi.
  • Morphological and ultrastructural evidence supports fungal classification.
  • Evidence indicates that latent Pneumocystis infection is unlikely in adults.

Conclusions:

  • Pneumocystis is classified as a fungus based on molecular and morphological data.
  • Adult Pneumocystis infections are likely acquired anew, not reactivated.
  • This finding necessitates a revised approach to infection prevention.

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