Medical Microbiology

OpportunisticMycoses(OM)

&Opportunisticmycoses(OM)thataffectskinandmucosaaswellasinter-

nalorgansarecausedbybothyeastandmolds.Apreconditionfordevelop-

mentofsuchinfectionsisapronouncedweaknessinthehost’simmunede-

fenses.Candidiasisisanendogenousinfection.OtherOMsareexogenousin-

fectionscausedbyfungithatnaturallyinhabitthesoilorplants.Theseen-

vironmentalfungiusuallyinvadeviatherespiratorytract.Themostimpor-

tantareaspergillosis,cryptococcosis,andthemucormycoses.BesidesCandi-

daandotheryeasts,phaeohyphomycetesandhyalohyphomycetes,whichare

onlyverymildlypathogenic,canalsocausesystemicinfections.AllOMshave

aprimaryinfectionfocus,usuallyintheupperorlowerrespiratorytract.

Fromthisfocus,thepathogenscandisseminatehematogenouslyand/orlym-

phogenouslytoinfectadditionalorgans.Infectionfocishouldberemoved

surgicallyiffeasible.Antimycoticagentsareusedinchemotherapy.Inin-

fectedimmunocompromisedpatients,theprognosisisusuallypoor. &

Candida(Soor)

Atleast 70 %ofallhumanCandidainfectionsarecausedbyC.albicans,therest

byC.parapsilosis,C.tropicalis,C.guillermondii,C.kruzei,andafewotherrare

Candidaspecies.

362 6 FungiasHumanPathogens

Candidaalbicans

5 μm

Yeast cells Pseudomycelium Mycelium

a 10 μm

b

Fig.6. 2 Candidaalbicans.

aMorphologicalforms.

bGramstainingofsputum:Gram-positiveyeastcellsandhyphae.

Clinicaldiagnosis:candidiasisoftherespiratorytract.

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Kayser, Medical Microbiology © 2005 Thieme