Medical Microbiology

GeneralAspectsofFungalDisease 353

chialasthma,orallergicalveolitis.Manyoftheseallergicreactionsarecerti-

fiedoccupationaldiseases,i.e.,“farmer’slung,”“woodworker’slung,”and

othertypesofextrinsicallergicalveolitis.

Mycotoxicoses

Somefungiproducemycotoxins,thebestknownofwhicharetheaflatoxins

producedbytheAspergillusspecies.Thesetoxinsareingestedwiththefood

stuffsonwhichthefungihavebeengrowing.AflatoxinB1maycontributeto

primaryhepaticcarcinoma,adiseaseobservedfrequentlyinAfricaand

SoutheastAsia.

Mycoses

Dataonthegeneralincidenceofmycoticinfectionscanonlybeapproximate,

sincethereisnorequirementthattheybereportedtothehealthauthorities.

Itcanbeassumedthatcutaneousmycosesareamongthemostfrequentin-

fectionsworldwide.Primaryandopportunisticmycosesare,ontheother

hand,relativelyrare.Opportunisticmycoseshavebeenontheincreaseinre-

centyearsanddecades,reflectingthefactthatclinicalmanifestationsare

onlyobservedinhostswhoseimmunedispositionallowsthemtodevelop.

Increasingnumbersofpatientswithimmunedefectsandahighfrequencyof

invasiveandaggressivemedicaltherapiesarethefactorscontributingtothe

increasingsignificanceofmycoses.Table5. 2 providesasummaryviewofthe

mostimportanthumanmycoses.Thecategorizationoftheinfectionsused

heredisregardstaxonomicconsiderationstoconcentrateonpracticalclinical

aspects.

Host-pathogeninteractions

Thefactorsthatdeterminetheonset,clinicalpicture,severity,andoutcomeof

amycosisincludeinteractionsbetweenfungalpathogenicityfactorsandhost

immunedefensemechanisms.Comparedwiththesituationinthefieldof

bacteriology,itmustbesaidthatwestillknowlittleabouttheunderlying

causesandmechanismsoffungalpathogenicity.

Humansshowhighlevelsofnonspecificresistancetomostfungibasedon

mechanical,humoral,andcellularfactors(seeTable 1. 6 ,p.22).Amongthese

factors,phagocytosisbyneutrophilicgranulocytesandmacrophagesisthe

mostimportant.Intensivecontactwithfungiresultsintheacquisitionofspe-

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Kayser, Medical Microbiology © 2005 Thieme