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TORTORA • FUNKE • CASE Microbiology AN INTRODUCTION EIGHTH EDITION B.E Pruitt & Jane J. Stein Eukaryotic Pathogens: Fungi PowerPoint® Lecture Slide Presentation prepared by Christine L. Case Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? • Fungi • Classification • Hyphae and multicellularity • Cell walls: sepatate or coenocytic hyphae • Spores: sexual or asexual • Unicellular Yeasts • Three-Four Major Medically Impt. Groups • Zygomycetes: Conjugation Molds • Ascomyctes: Sac Fungi • Basidomycetes: Club Fungi • Fungal Diseases: Mycoses • Aspergillosis, histoplasmosis, candidiasis, etc • Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells. The Fungi • Eukaryotic • Aerobic or facultatively anaerobic • Chemoheterotrophic • Most are decomposers • Mildly acidophilic, acid tolerant • More osmotically tolerant than bacteria • Mycology is the study of fungi Fungi Table 12.1 Molds • Molds consist of hyphae; a mass of hyphae is a mycelium. 1 hypha Mycelium Figure 12.2 Key Characteristics: Cell Walls, Spore Types (Aseptate) Sometimes hyphal cells are dikaryotic Types of Spores: Asexual or Sexual Zygomycota Zygospores (sexual) Zygomycota Ascomycota Ascomycota, Basidiomycota Conidiospores (asex.) Ascospores (sexual) Basidiomycota Basidospores (sexual) Sporangiospores (asex.) Sexual spores arise from meiosis Asexual spores arise from mitosis Yeasts : Single-celled Fungi • Unicellular fungi, ovid • Fission yeasts divide symmetrically • Budding yeasts divide asymmetrically • Mycoses: Candidiasis (local and systemic) from Candida albicans • Beneficial: Saccharomyces cerevesiae/baker’s yeast Figure 12.3 Dimorphism • Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C Figure 12.4 Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? • Fungi • Classification • Hyphae and multicellularity • Cell walls: sepatate or coenocytic hyphae • Spores: sexual or asexual • Unicellular Yeasts • Three-Four Major Medically Impt. Groups • Zygomycetes: Conjugation Molds • Ascomyctes: Sac Fungi • Basidomycetes: Club Fungi • Fungal Diseases: Mycoses • Aspergillosis, histoplasmosis, candidiasis, etc • Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells. Zygomycete Life Cycle: Conjugation Molds •Coenocytic hyphae. Produces sporangiospores and zygospores •E.g. Rhizopus/black bread mold Figure 12.6 Ascomycete Life Cycle: The Sac Fungi •Septate hyphae. Produces ascospores or conidiospores •Systemic mycoses: Aspergillosis , histoplasmosis, penicilliasis •Cutaneous mycoses: Microsporum/Trichophyton (jock itch, athlete’s foot, ringworm) Basidiomycete Life Cycle: Club Fungi •Septate hyphae. Produces basidiospores and sometimes conidiospores. • Cryptococcus neoformans (systematic mycosis) • Toxic Mushrooms (Amanita) Figure 12.8 Lichens: Ascomycete with unicellular algae or cyanobacteria Figure 12.10 Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? • Fungi • Classification • Hyphae and multicellularity • Cell walls: sepatate or coenocytic hyphae • Spores: sexual or asexual • Unicellular Yeasts • Three-Four Major Medically Impt. Groups • Zygomycetes: Conjugation Molds • Ascomyctes: Sac Fungi • Basidomycetes: Club Fungi • Fungal Diseases: Mycoses • Aspergillosis, histoplasmosis, candidiasis, etc • Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells. Aspergillosis (Aspergillus mold) respiratory or systemic Ascomycete •Most commonly seen in immunocompromised patients •May start in lungs as fungus ball or in sinuses •Can become systemic (esp. in AIDS); endocarditis (valves) •Bronchiectasis (scarring of bronchioles) •Prefers aerobic environment •Asthmatics may be allergic to mold spores •Found in dead and decomposing plant material in nature •Treated with amphotericin B; allergics with prednisone Candidiasis caused by Candida albicans yeast Ascomycete Vaginitis (“vaginal yeast infection”) Systemic candidiasis, often in AIDS patients Treated with antifungals like nystatin Thrush Histoplasmosis (Histoplasma capsulatum) Ascomycete • Dimorphic: both yeast-like and mold-like • Mild respiratory infection • Acquired from airborne spores often in bird and bat feces •Mostly immunocompromised patients; AIDS •Often not treated, otherwise with amphotericin B Pneumocystis pneumonia (Pneumocystis jurovecii) •Yeast-like and protozoan-like •Hard to culture and classify •Pathogenic in immunosuppressed individuals (e.g. AIDS) •Forms cysts in the lungs that rupture to release more cells •Causes pneumonia •Human-based organism only •In its own group: Deuteromycota Skin mycoses Usually caused by Trichophyton, Microsporum, or Epidermophyton • Tinea pedis (athlete’s foot) • Tinea corporis or capitis (ringworm) • Tinea cruris (jock itch) All are ascomycetes Epidermophyton Microsporum Eukaryotic Pathogens: Fungi What types of eukaryotic organisms are pathogenic, and how do they differ from bacteria? • Fungi • Classification • Hyphae and multicellularity • Cell walls: sepatate or coenocytic hyphae • Spores: sexual or asexual • Unicellular Yeasts • Three-Four Major Medically Impt. Groups • Zygomycetes: Conjugation Molds • Ascomyctes: Sac Fungi • Basidomycetes: Club Fungi • Fungal Diseases: Mycoses • Aspergillosis, histoplasmosis, candidiasis, etc • Better Adaptation to Hostile Environments Eukaryotic pathogens are mostly parasitic and are difficult to target selectively with drugs since their cells are so similar to human cells. Fungi vs Bacteria (Mycosterols) , genatmycin Sugar or salt tolerance More tolerant of high osmotic environments (grows more easily on jams and jellies) Less tolerant of high osmotic envir. Acid tolerance More tolerant of acidic environments (can culture on Sabourad agar) Less tolerant of acidic environments Moisture tolerance Tolerant of low moisture environments (can grow on shoe leather!) Requiring higher moisture environments Nitrogen requirements Require less nitrogen Require more nitrogen Carbohydrate produce Produces indigestible carbohydrates Can digest plant carbohydrates Most carbohydrates produced are digestible Can’t digest some plant carbos.
