Opportunistic Fungal PathogensAspergillusPowerPoint PresentationSlide 4Slide 5Polarized GrowthSlide 7Nutritional Versatility and ThermotoleranceDisease States Associated with A. fumigatus InfectionSlide 10Slide 11Pathogenesis of Invasive AspergillosisSlide 13AngioinvasionSlide 15Incidence of Invasive AspergillosisCryptococcus neoformansSlide 18Slide 19Slide 20Slide 21Slide 22CryptococcosisSlide 24Slide 25Endemic Fungal PathogensComaprisonsOpportunistic Fungal Pathogens….continuedAspergillus •Named in 1727 by a priest for its resemblance to a holy water sprinkler (Aspergillum).•Genus contains over 200 species•Many are used for industrial purposes (pharmaceuticals)•Used for fermentation of soybean (miso and soy sauce) and sake (rice wine).David Gregory and Debbie Marshall, Wellcome ImagesAnnual Review of Microbiology Vol. 56: 433-455 Pihet et al. BMC Microbiology 2009 9:177 doi:10.1186/1471-2180-9-177Conidia:•Vehicle for environmental dissemination•Metabolically inactive•Dessication resistant•UV resistant•Heat resistant•HydrophobicThe 1-2um size of A. fumigatus conidia allows for deep penetration into the human alveolar spaces. The hydrophobic properties are conferred by roldet proteins encoded by rodA and rodB. rodA and rodB knockouts are hypersensitive to killing by alveolar macrophages.The rodlet layer renders A. fumigatus spores immunologically inertA.fumigatus conidiophores A. fumigatus grown on minimal mediumIsotropic GrowthGerminationPolarized growth and SeptationProduction of foot cell and aerial hyphaeClavate vesicle developmentConidiophore development and conidiationwt rodBrodA rodA rodBAppl Environ Microbiol. 2003 Mar;69(3):1581-8.Polarized Growth•Hyphal extension occurs from the tip•Specialized organelles control hyphal growth•Spitzenkorper•Polarisome•Sterol-rich lipid rafts accumulate at the hyphal tip•Molecular motors bring vesicles containing necessary elements for cell wall synthesis and membrane synthesis.•Much of the active endocytosis also occurs at the hyphal tip.Steinberg, G.. 2007. Eukaryotic Cell 6(3):351-360FIG. 7. A model of hyphal tip growthNutritional Versatility and Thermotolerance•The fundamental role of filamentous fungi is the recycling of environmental C and N•A. fumigatus is the predominant fungus during the high temperature phases of compostingTemperatureMesophilic FungiThermophilic Fungiww.fao.org/docrep/007/y5104e/y5104e00.gif•Fungus Ball / Aspergilloma–Growth of A. fumigatus in airways without invasion–Can lead to bleeding–Can occur in healthy patientsAspergillomaDisease States Associated with A. fumigatus Infection•Allergic Bronchopulmonary Aspergillosis (ABPA)•Colonization of the lung resulting in chronic inflammation and lung fibrosisDisease States Associated with A. fumigatus InfectionPre24 hr48 hrThe Journal of Immunology, 1999, 162: 6071-6079.•Invasive Aspergillosis•Can be relegated to the lung•Often disseminates hematogenously•A. fumigatus can grow irrespective of anatomical boundariesDisease States Associated with A. fumigatus InfectionPMID: 20974273Pathogenesis of Invasive AspergillosisPMID: 20974273Pathogenesis of Invasive AspergillosisAngioinvasionPMID: 20974273Pathogenesis of Invasive AspergillosisIncidence of Invasive AspergillosisHarrison's Internal Medicine , Chapter 197. AspergillosisCryptococcus neoformansBasidiomcetous yeast-like fungus•yeast cells are surrounded by a thick polysaccharide capsule•pathogenic strains grow well at 37oC.•Produce laccase - a multi-copper oxidase that is required for virulence of some strains.TaxonomyC. neoformans var. grubii - Serotype AMost common clinical isolate in US and AfricaFound in bird excretaC. gatii - Serotypes B and CPreviously limited to tropic/subtropic but recently found on Vancouver IslandInfects mainly immunocompetent hostsC. neoformans var. neoformans - Serotype DCommon in parts of EuropeAlso found in bird excretaGXMGalXMInfection by C. neoformans•Seroconversion for most individuals occurs before the age of 10•Three possible outcomes of infection:•Clearance of infection•Development of latent infection•Acute infection with or without dissemination (Cryptococcosis)•Outcome depends on strain, inoculum and immune status of the host•Pneumonia•Meningo-encephalitis•600,000 deaths/year, mainly in Sub-Saharan Africa and Southeast AsiaCryptococcosis•Clinical Presentation–the lung is the initial portal of entry•benign colonization to severe pneumonia•severely immunocompromised patients may not exhibit any pulmonary symptoms due to rapid dissemination of the infection to the CNS–meningoencephalitis•most common presentation of cryptococcosis•patients present with headache, fever and altered mental status•fatal if untreated–dissemination (outside of CNS)•Skin–nearly all types of skin lesions have been reported for C. neoformans infection•Eye–45% of meningoencephalitis patients have ocular signs and symptoms•dissemination to nearly every organ system, bone and muscle has been reported•fungemia detected in the severely immunocompromised–immune reconstitution syndrome•Some patients upon immune reconstitution will develop symptoms of meningoencephalitis•believed to be a response to latent or silent infection, or to polysaccharide antigenCryptococcosis•Laboratory diagnosis–Microscopic examination•Indian ink stain of CSF from lumbar puncture–Large polysaccharide capsule excludes stain•Mucicarmine stain of tissue - –Capsule will stain red–Serologic test •latex agglutination test for cryptococcal polysaccharide•Treatment–Amphotericin B + flucytosine initally, followed by fluconazole–Treatment with AmB required monitoring of patient electrolytes and cannot be accomplished without appropriate infrastructure.–High-dose fluconzole therapy is being used in Africa with limited success.–Emergence of fluconazole resistant strains.Endemic Fungal Pathogens•Thermal dimorphism:–At 25o C, they are filamentous (mould)–At 37o C, they are yeast-like•Geographical limitation–They each have specific geographical regions where they are found, hence the term endemic.•All cause pulmonary infection that ranges from mild to severe depending on host immune status and size of exposure.ComaprisonsBlastomyces dermatitidis•Extracellular yeast•Endemic to upper midwestHistoplasma capsulatum•Intracellular yeast•Endemic to Ohio and Mississippi River