Medical Microbiology

areinhaledandenterthelungs,resultinginapulmonarycryptococcosisthat

usuallyrunsaninapparentclinicalcourse.Fromtheprimarypulmonaryfoci,

thepathogensspreadhematogenouslytootherorgans,aboveallintothecen-

tralnervoussystem(CNS),forwhichcompartmentC.neoformansshowsa

pronouncedaffinity.Adangerousmeningoencephalitisistheresult.Good

preconditionsfordisseminationfromthelungfociareprovidedespecially

byprimarydiseasesthatweakentheimmunedefenses.Malignanciesand

steroidtherapyareotherfrequentpredisposingfactors.AIDSpatientsalso

frequentlydevelopcryptococcoses.

Diagnosis.Thisisparticularlyimportantinmeningitis.Thepathogenscanbe

detectedincerebrospinalfluidsedimentusingphasecontrastmicroscopy.An

inkpreparationresultsinanegativeimageofthecapsule(seeFig.6.5a).Cul-

turingismostsuccessfulonSabouraudagar.C.neoformanscanbedifferen-

tiatedfromotheryeastsandidentifiedbasedonspecialmetabolicproperties

(e.g.,breakdownofurea).Alatexagglutinationtestisavailablefordetection

ofcapsulepolysaccharideincerebrospinalfluidandserum(anticapsular

antibodiescoupledtolatexparticles).Identificationofantibodiestothecap-

sularpolysaccharideisachievedbymeansofanagglutinationtestoranen-

zymaticimmunosorbencetest.

Therapy.AmphotericinBistheagentofchoiceinCNScryptococcosis,often

usedincombinationwith5-fluorocytosine.

Epidemiologyandprevention.Noprecisefiguresareavailableonthefre-

quencyofpulmonarycryptococcosis.Theincidenceoftheattendantmenin-

goencephalitisisonecasepermillioninhabitantsperyear.Therearenospe-

cificprophylacticmeasures.

Mucor,Absidia,Rhizopus(Mucormycoses)

MucormycosesarecausedmainlybyvariousspeciesinthegeneraMucor,

Absidia,andRhizopus.Morerarely,thistypeofopportunisticmycosisis

causedbyspeciesinthegeneraCunninghamella,Rhizomucor,andothers.

AllofthesefungalgeneraareintheorderMucoralesandoccurubiquitously.

Theyarefoundespeciallyoftenondisintegratingorganicplantmaterials.

Morphologyandculture.Mucoralesaremoldsthatproducebroad,nonsep-

tatehyphaewiththickwallsthatbranchoffnearlyatrightangles(Fig.6. 6 ).

Mucoralesarereadilycultured.Theygrowonallstandardmediums,forming

high,whitish-graytobrown,“fuzzy”aerialmycelium.

CulturingisbestdoneonSabouraudagar.

Pathogenesisandclinicalpictures.Mucoralesaretypicalopportuniststhat

onlycauseinfectionsinpatientswithimmunedeficienciesormetabolicdis-

OpportunisticMycoses(OM) 367

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Kayser, Medical Microbiology © 2005 Thieme