This document discusses Pneumocystis carinii, an opportunistic pathogen that causes pneumonia in immunocompromised individuals. It is unclear whether P. carinii is a fungus or protozoan, as it exhibits characteristics of both. It is found worldwide and infects humans and other mammals. Transmission occurs through aerosol droplets or direct contact. The life cycle involves asexual and sexual reproduction through trophozoite, cyst, and sporozoite forms. Infection causes pneumonitis and pneumonia. Diagnosis involves staining of sputum or bronchial samples. Treatment includes TMP-SMZ antibiotics and corticosteroids.

1. Pneumocystis carinii

2. Introduction
 Fungus or Protozoan??
 Orphan organism, phylogenic position has not
yet been established
 Opportunistic Parasite
 Severe pathology in immunodeficient hosts
Severely malnourished newborns
 One of the initial signs of AIDS emergence
 Lives in interstitial tissue of lungs
 Rarely disseminates to spleen, lymph nodes, bone
marrow, eyes

3. Fungus vs. Protozoan
 Fungus
 from nucleic acid and
biochemical analysis
 rRNA homologous to
that found in fungi
 stains with some
fungal stains
 Affinity for Grocott’s
methenamine silver stain
 Produces chitin
 has ultrastructural
characteristics similar
to some fungi
 Protozoan
 other structures
similar to Toxoplasma
and Plasmodium
 is sensitive to a
variety of
antiprotozoal agents.
 It’s membrane
properties resemble
those of amebas
 Shows surface
antigenic variation
which occurs in
protozoa and has not
been established in
fungi

4. Geographic Distribution
 Worldwide
 Most children exposed by the age of 3-4 years
 Commonly found in the lungs of healthy individuals, but
no disease occurs
 Widespread in mammals

5. Hosts
 Humans
 Pneumocystis jiroveci(i) alternate names
 Pneumocystis carinii hominis
 Elderly, malnourished children, primary
immunodeficiency disorders, AIDS
 Patients receiving cytotoxic or
immunosupressive drugs for lymphoresticular
cancers or transplants
 Other mammals: rabbits, dogs, goats, swine, cats,
chimpanzees, owl monkeys, horses

6. Transmission
 Aerosol droplets
 Direct contact
 Congenital infection
 Household pets
 Reactivation of latent infection when
immunocompromised
 Or, new infection?

7. Life Cycle
 Life cycle is not fully known
 Asexual and sexual reproduction (CDC)
 Four general morphological forms in mammals
 Trophozoite (has amoeboid trophozoite form)
 Precysts
 Cysts
 Sporozoites (intracystic bodies)
 Cyst (diagnostic form)
 chitinous membrane and 8 intracystic bodies
 Pore in cyst wall used for releasing sporozoites.
 Can be spherical or collapsed.

8. Life Cycle

10. Clinical Presentation
 Causes Pneumonitis, Pneumocystis pneumonia (PCP)
 Lung epithelium becomes desquamated
 alveoli fill with foamy exudate containing parasites
 Fever, non productive cough, breathing difficulty on
exertion, respiratory failure, cyanosis
 Death by asphyxia

11. Diagnosis
 Clinical symptoms
 Sputum or bronchial lavage
 Special staining with toluidine blue, methenamine
silver
 Gram-Weigert stain for cysts
 ELISA, immunofluorescence assay, DNA amplification
being developed

12. Diagnosis

13. Pictures
 Trophozoites in BAL
material.
 Cysts in BAL
material

14. Treatments
 Trimethoprim-sulfamethoxazole (TMP-SMZ)
 Pentamidine isethionate inhalant
 Treatments can be toxic and patient must be
monitored closely
 Prophylactic treatment if CD4 count is low (<200)
 HAART regimen to boost immune system function,
corticosteroids