Presentation on theme: "Dental / Optometry Fundamentals II Stephen A. Moser, Ph.D. 10/26/2011"— Presentation transcript:
1 Dental / Optometry Fundamentals II Stephen A. Moser, Ph.D. 10/26/2011 MycologyDental / Optometry Fundamentals IIStephen A. Moser, Ph.D.10/26/2011
2 Epidemiology Geography Transmission of infection Endemic mycoses Worldwide mycosesTransmission of infectionRespiratory inhalation (systemic mycoses)Cutaneous inoculation (sporotrichosis)Systemic invasion by opportunistic normal flora (candidiasis)Contact with infected hosts (dermatophytoses)
3 Epidemiology (Cont.) Risk factors and manifestations of disease True pathogens versus opportunistsEnvironmental risk factors for systemic fungal diseaseLocation and travelOccupationHost defenses and susceptibility to systemic fungal disease (CMI most important)Congenital and acquired T cell deficiencies (including AIDS)Immunosuppression (transplants and malignancies)Diabetes mellitus
5 General Characteristics Aerobic - obligate or facultativeEukaryotic: membrane bound nucleus and cytoplasmic organelles (may be multinucleate)AchlorophyllousMorphology (unicellular or multicellular)Saprophytic (heterotrophic)
6 Characteristics of Fungal Cells Cell wall: multilayered polysaccharideCellulose, glucans, mannans, chitin, polypeptidesAbsence of teichoic acids, peptidoglycan, LPSCell membranePhospholipid bilayerErgosterol (relate to chemotherapy)Cytoplasm - typical eukaryotic organellesNucleus - either uninucleate or multinucleate
7 Characteristics of Fungal Cells CapsulePresent in some species (e.G. Cryptococcus neoformans)Amorphous polysaccharide coatingFunctions and activitiesAntiphagocyticAntigenic
8 Characteristics of Fungal Cells Growth formsYeast - unicellular fungi which reproduce by budding (Cryptococcus)Mold - hyphae (mycelium)Septate hyphae (Aspergillus)Non-septate, coenocytic hyphae (Mucor)Pseudohyphae (Candida albicans)Thermal dimorphism
14 Asexual Reproduction Conidia (spores) – asexual structures Blastospores – formed by budding yeasts (Blastomyces)Chlamydospores – terminal or intercalary cells with thick walls (Candida albicans)Arthrospores – formed by fragmentation of hyphae (Coccidioides immitis)Sproangiospores – formed in sporangia by cleavage (Rhizopus)
15 Classification Based on Sexual Phase Ascomycetes: Aspergillus, Histoplasma, Blastomyces, DermatophytesBasidiomycetes: Cryptococcus, MushroomsZygomycetes: Order Mucorales - Mucor, RhizopusDeuteromycetes (Fungi Imperfecti): Sporothrix, Coccidioides, Candida
17 Routes of Infection Inhalation of spores – major factor Inoculation of spores into skinDisease by normal flora in compromised host (Candida)HypersensitivityContact with infected host (Dermatophytes)Mycotoxins
18 Laboratory Diagnosis of Fungal Infections Microscopic Examination of tissues and body fluidsGram stainGiemsaIndia InkPotassium hydroxide (KOH) wet prepHematoxylin and Eosin stainPeriodic-Acid Schiff stain (PAS)Gomori-Methenamine Silver stain (GMS)Mucicarmine or Alcian Blue stain
25 Histopathological Response to Fungal Infection Acute pyogenic abscess (Candida)Chronic granuloma formation (Histoplasma)Chronic, localized dermal inflammation (Dermatophytes)Mixed pyogenic and granulomatous inflammation (Blastomyces)Blood vessel invasion with thrombosis and infarction (Mucor, Aspergillus)Hypersensitivity without tissue reaction (allergic bronchopulmonary aspergillosis)
26 Fungal Cultures Utilize Sabouraud agar with antibiotics Identification criteriaTemperature of growthRate of growthColonial and microscopic morphologySporulation patternBiochemical reactions (yeast)
27 Fungal SerologyGenerally poor and not as useful as in other pathogens such as viruses and bacteria, with some exceptions.Cryptococcal antigen by latex agglutination: serum and CSF.Coccidioides - early IgM response is useful for identification of acute primary disease - CSF IgG prognostic value.Skin tests for DTH - problems:Cross-reactivity.High positive rate in endemic areas.
51 Antifungal Drugs for Systemic Mycoses - Amphotericin B Mode of ActionBinds to ergosterol, increases membrane permeability resulting in leakage of cytoplasmic components and cell death – FungicidalSpectrum of ActivityCandida, Crypto, Aspergillus, Histo, Blasto, Cocci, etcLimitationsNephrotoxicity
52 Antifungal Drugs for Systemic Mycoses - Fluconazole Mode of ActionPrevents ergosterol synthesis by inhibiting the C-14 demethylation step (cytochrome P-450 rx)FungistaticSpectrum of ActivityCandida, Crypto, Trichsporonosis, dermatophytesLimitationsResistance in some Candida sp – krusei and glabrataNot effective for non-dermatophyte moulds.
53 Antifungal Drugs for Systemic Mycoses -Echinocandins Mode of ActionPrevents synthesis of beta 1,3-glucan required for cell wall.FungistaticSpectrum of activityAspergillus, CandidaNOT effective against Cryptococcus, zygomycetes.
54 Early Diagnosis of Invasive Fungal Infections ObstaclesBecause of Immunosuppression typical signs and symptoms of infection are frequently absentFew clinical features are uniquely specific for systemic fungal infectionSputum and blood cultures are frequently negativeInvasive proceduresMay be necessary for definitive diagnosisAre often complicated in severely immunocompromised patient
55 Early Diagnosis of Invasive Fungal Infections (Continued) BenefitsEarly diagnosis permits selection of a therapy of maximal effectivenessEarly intervention with antifungal therapy may help decrease the high mortality rate associated with serious systemic mycoses
56 Major Areas Covered How fungi differ from bacteria The major fungal infectionsThe epidemiology of fungal infectionsPathology of fungal infectionsMechanism of action of antifungal agents