LUNG PARASITES
INCERTAE SEDIS

PNEUMOCYSTIS JIROVECI (P.CARINII)

pc1-ic

P.jiroveci: the infection has a world-wide distribution 
and the transmission seems to occur by airborne route.
The organims that causes human pneumocystosis is 
now named Pneumocystis jiroveci * Frenkel 1999, 
in honor of the Czech parasitologist Otto Jirovec. 
The organism is now considered a fungus, 
based on nucelic acid and biochemical analysis; nevertheless, 
on the basis of morpholocic and biologic characterisitcs 
it is included in the atlas of medical parasitology.
* J.R. Stringer, C.B. Beard, R.F. Miller, A.E. Wakefield 
Emerging Infectious Diseases 2002vol. 8, No 9:891-896
Life cycle.

pc2-ic

Pneumocystosis is one of the most common infections in
immunosuppressed patients with AIDS.
Other impairements of cellular immunity such as primary immunodeficiencies,
steroid treatment, organ transplantation and cancers predispose to P.c. infection.
This typical chest roentgenogram shows diffuse bilater
interstitial infiltrates from the hilar region.

pc3-ic

P.jiroveci: infiltrates are usually diffuse but atypical presentations can occur:
nodules, cavitation, consolidation, pneumatocele and pneumotorax.

pc4-ic

P.jiroveci: after inhalation the microorganism reaches the alveoli
and adheres to the type I pneumocytes.
The trophozoites then multiply slowly but extensively in the lungs and
progressively fill the alveoli that are finally stuffed by the foamy exudate.
The classical exudate consists of clusters of P.jiroveci, degenerated cells,
host proteins and few alveolar macrophages.
H&E stain.

pc5-ic

P.jiroveci: in tissue sections obtained with open lung biopsy or at autopsy
the alveolar space appears filled by honeycombed material consisting in clusters
of P.jiroveci, host proteins and degenerated cells. A scanty inflammation is present.
As the disease progresses interstitial hyperplasia with edema and infiltration occur.
H&E stain.

pc6-ic

P.jiroveci: clusters of cysts are demonstrated in the alveolar space
with stains which are selective for the "parasite" wall: methenamine silver
and toluidine blue O. Open lung biopsy, silver methenamine stain.

pc7-ic

P.jiroveci: clusters of cysts are demonstrated in the alveolar space.
Open lung biopsy, silver methenamine stain.

pc8-ic

P.jiroveci: with higher magnification single cysts are visible within the cluster.
Open lung biopsy, silver methenamine stain.

pc9-ic

P.jiroveci diagnosis: fiberoptic bronchoscopy with BAL is actually
the most commonly used diagnostic procedure.
The diagnosis is based on the observation of cysts and trophozoites.
Clusters of P.jiroveci can be observed in wet mount preparations.

pc10-ic

P.jiroveci: at higher magnification cysts with intracystic bodies
can be detected within the clusters.
(Wet-mount preparations).

pc11-ic

P.jiroveci: empty, collapsed and filled cysts cohexist inside the cluster and
can be observed with oil immersion.
(Wet-mount preparations)

pc13-ic

P.jiroveci: the bronchoalveolar lavage can be stained with specific stains
for trophozoites like Giemsa. Clusters of typical pleomorphic trophozoites
(1-3 micron) and cysts can be observed:
trophic forms appear with reddish nuclei and blue cytoplasm.

pc14-ic

P.jiroveci: with Giemsa stain cysts (approx. 5-8 µm in diameter) are variably stained.
Intracystic bodies are present in different numbers within the cysts.
Mature cysts have 8 intracystic bodies. Some cysts appear empty.

pc15-ic

P.jiroveci: cysts have a thick wall: sometimes the wall appears as a transparent
outline with intracystic bodies.

pc16-ic

P.jiroveci: the sediment of the BAL can be stained with stains for
the cysts wall such as methenamine silver.
The cysts are well recognizable as round, 
oval or flat bodies of approx. 4-5 µm in diameter.
Gomori's methenamine silver stain (GMS).

pc17-ic

P.jiroveci: fungi have the same affinity for silver methenamine and
can be confused with P.jiroveci cysts. Cryptococcus neoformans in a BAL specimen.
(GMS stain).

pc18-ic

P.jiroveci: toluidine blue O stains the cysts wall as silver methenamine.
Clusters of P.jiroveci are composed of cysts in different stage of development
(empty, collapsed and mature cysts). Toluidine blue O stain.

pc19-ic

P.jiroveci: sometimes with toluidine blue O some clusters appear as
honeycombed material containing few cysts.
Toluidine blue O stain.

pcc19-ic

P.jiroveci: crowded and collapsed empty cysts 4 µm in diameter. 
Cyst wall is blue. Bronchoalveolar lavage from a patient suffering from AIDS.
 Gram-Weigert stain. 
Objective 100 X

pcpsk-ic

P_jiroveci_1.ic P.jiroveci_Direct_ fluorescence1

P.jiroveci: indirect immunofluorescence 
using monoclonal antibodies, FITC coupled, 
is a sensitive and specific technique of diagnosis.

pc20-ic

P.jiroveci: with transmission electron microscopy (TEM) clusters of P.jiroveci
appear composed of cysts in different stages of development, of empty,
collapsed cysts and of trophozoites.
(TEM, 2.200 X).

pc21-ic

P.jiroveci: with transmission electron microscopy cysts show
a thick wall and the intracystic bodies a nucleus and mitochondria.
(TEM, 11.500 X).

pc22-ic

P.jiroveci: collapsed cyst within a cluster of P.jiroveci. (TEM, 15.500 X).