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Pneumocystis carinii. Taxonomy as viewed by electron microscopy

A ul Haque, S B Plattner, R T Cook

    American Journal of Clinical Pathology
    |April 1, 1987
    PubMed

    Insights

    Pneumocystis carinii, an opportunistic pathogen, shows fungal characteristics. Ultrastructural analysis suggests it is a primitive fungus, not a protozoan, despite its unicellular form.

    Area of Science:

    • Microbiology
    • Mycology
    • Infectious Diseases

    Background:

    • Pneumocystis carinii is an opportunistic pathogen causing pulmonary infections in immunocompromised individuals.
    • The classification of P. carinii remains debated, with its taxonomic status unresolved.

    Purpose of the Study:

    • To investigate the ultrastructure of P. carinii using transmission and scanning electron microscopy.
    • To provide evidence for the classification of P. carinii.

    Main Methods:

    • Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used.
    • Analysis of lung tissue samples from two patients with P. carinii pulmonary infections.

    Main Results:

    • Organisms exhibited variable shapes and sizes, dividing by binary fission.
    • Absence of motility organelles, Golgi apparatus, phagosomes, and lysosomes was noted.
    • Poorly developed mitochondria and endoplasmic reticulum, with asynchronous nuclear and cytoplasmic development.

    Conclusions:

    • Ultrastructural evidence supports P. carinii being a primitive fungus, not a protozoan.
    • The organism may represent a unicellular state of a fungus with preserved sporulation ability.

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