Medical Microbiology

opment,thecyst.Thecyststhenreleasethespores,whichinturndevelop

intotrophozoites.

Culture.P.cariniicannotbegrowninnutrientmediums.Itcangothrougha

maximumof 10 developmentalcyclesincellcultures.Sufficientpropagation

isonlypossibleinexperimentalanimals,e.g.,rats.Thismakesitdifficultto

studythepathogen’sbiologyandthepathogenicprocessandexplainswhyall

aspectsoftheseinfectionshavenotyetbeenclarified.

Pathogenesisandclinicalpictures.Humansshowconsiderableresistanceto

P.cariniiinfections,whichexplainswhyabouttwo-thirdsofthepopulaceare

eithercarriersorhaveahistoryofcontactwiththeorganism.Diseaseonly

becomesmanifestinthepresenceofdefectsinthecellularimmunesystem.

Ofprimaryconcernamongtheclinicalmanifestationsistheinterstitial

pneumonia.Profuseproliferationofthepathogeninthealveolidamages

thealveolarepithelium.Thepathogensthenpenetrateintotheinterstitium,

wheretheycausethepneumonia.Startingfromtheprimaryinfectionfoci,

thefungispreadtootherorgansin 1 – 2 %ofcases,causingextrapulmonary

P.cariniiinfections(ofthemiddleear,eye,CNS,liver,pancreas,etc.).

Diagnosis.Suitabletypesofdiagnosticmaterialincludepulmonarybiopsies

orbronchoalveolarlavage(BAL)specimensfromtheaffectedlungsegments.

GrocottsilverstainingcanbeusedtorevealcystsandGiemsastainingshows

uptrophozoitesandsporozoites.Directimmunofluorescence,withlabeled

monoclonalantibodiestoasurfaceantigenofthecysts,facilitatesdetection

OpportunisticMycoses(OM) 371

Cryptococcusneoformans

a b c

20 μm 10 μm 21 μm

Fig.6. 7 aCystsofP.carinii,Grocottstaining.

bYeastfungi,Grocottstaining(fordifferentialdiagnosis).

cCystsofP.carinii,detectionwithdirectimmunofluorescenceandmonoclonal

antibodies.

6

Kayser, Medical Microbiology © 2005 Thieme