Medical Microbiology

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clinicalandtherapeuticterms,theyarethesameascandidiasis.Malassezia
furfuroccasionallycausescathetersepsisinprematureneonatesandpersons
whohavetobefedlipidsparenterally.Lipidsencouragegrowthofthisyeast.
Penicilliosis.ThisfungalinfectioniscausedbythedimorphicfungusPenicil-
liummarneffei,whichprobablyinhabitsthesoil.P.marneffeiinfectionsare
oneofthemostopportunisticinfectionsmostfrequentlyseeninAIDSpa-
tientswhoeitherliveinSoutheastAsiaorhavestayedinthatareaforawhile.
Theinfectionfociarelocatedprimarilyinthelungs,fromwheredissemina-
tiontootherorganscantakeplace.Thetherapeuticofchoiceintheacute
phaseisamphotericinB,thistreatmentmustbefollowedbylong-termpro-
phylacticazoles(itraconazole)topreventremission.

Pneumocystiscarinii(Pneumocystosis)


&Pneumocystiscariniiisasingle-celled,eukaryoticmicroorganismthatwas
originallyclassifiedasaprotozoan,butisnowconsideredafungus.This
pathogencancausepneumoniainpersonswithdefectivecellularimmune
systems,inparticularthoseshowingAIDS.Extrapulmonarymanifestations
arealsorecordedinasmallnumberofcases.Laboratorydiagnosticmethods
includedirectdetectionofthemicrobesunderthemicroscope,bymeansof
directimmunofluorescenceorPCR.Appropriateanti-infectiveagentsfor
therapy includecotrimoxazole, pentamidine, or a combination ofthe
two. &

Pneumocystiscariniiisasingle-celled,eukaryoticmicroorganismthatwas,
untilrecently,classifiedwiththeprotozoans.MolecularDNAanalysishasre-
vealedthatitresemblesfungimorethanitdoesprotozoans,althoughsomeof
thecharacteristicpropertiesoffungi,suchasmembraneergosterol,aremiss-
inginPneumocystiscarinii.Thismicrobeoccursinthelungsofmanymam-
malianspeciesincludinghumanswithoutcausingdiseaseinthecarriers.
Clinicallymanifestinfectionsemergeinthepresenceofsevereunderlying
defectsincellularimmunity,asinAIDS.
Morphologyanddevelopmentalcycle.Threedevelopmentalstagesare
knownforP.carinii.Thetrophozoitesareellipticalcellswithadiameter
of 1 .5– 5 lm.Presumably,thetrophicformreproducesbymeansofbinary
transversefission,i.e.,asexually.Sexualreproductiondoesnotbeginuntil
twohaploidtrophozoitesfusetomakeonediploidsporozoite(orprecyst),
whichareconsideredtobeanintermediatestageinsexualreproduction.
Afterfurthernucleardivisions,thesporozoitespossesseightnucleiatthe
endoftheirdevelopment.Thenucleithencompartmentalizetoformeight
sporeswithadiameterof 1 – 2 lmeach,resultinginthethirdstageofdevel-

370 6 FungiasHumanPathogens

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Kayser, Medical Microbiology © 2005 Thieme
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