Transcript Fungi
Fungi (Chapter 28) “a group of diverse and widespread unicellular and multicellular organisms, lacking chlorophyll, usually bearing spores and often filamentous” Fungal Infections • last 10 years incidence of serious fungal infections has been increasing • nosocomial in nature and impacting the immunocompromised • need organic compounds and carbon: energy • aerobic or facultatively anaerobic Categories of Fungi • Page 410 • 1) yeasts • 2) molds • 3) dimorphic fungi Yeasts • spherical or oval Figure 28-1 • “budding”: parent cell forms a protuberance • parent cell’s nucleus divides and one nucleus migrates into the “bud” • 1 yeast cell can produce up to 24 daughter cells by “budding” • “buds” may form a short chain of cells Molds • thallus (body) • hyphae (filaments) • septa (cross-walls) • septate hyphae: hyphae that contain septa Dimorphic Fungi • 2 forms of growth in pathogenic species – 1) mold – 2) yeast • Mold: hyphae (multicellular) • Yeast: buds (unicellular) Dermatomycosis • Page 411 • caused by dermatophytes • infect the epidermis, hair, and nails • secrete enzyme: keratinase (degrades keratin, protein found in hair, skin and nails) • direct contact, infected hairs and epidermal cells (barber shop clippings, shower room floors) • 3 genera: Trichophyton, Microsporum, Epidermophyton Dermatomycosis (cont’d) • • • • • 3 genera: Trichophyton: infect hair, skin or nails Microsporum: infects hair or skin Epidermophyton: infects skin and nails Examples of infection: tinea capitis tinea cruris tinea pedis • Color Plates: 67 and 68 Coccidioidomycosis • respiratory disease caused by the fungus Coccidioides immitis (extremely virulent) • Spores found in dry, alkaline soils in the American Southwest, Mexico and S. America • wind carries the spores and transmits the infection (passing through endemic areas can lead to infection) • AKA: Posada-Wernicke disease, cocciodioidal granuloma, Valley/California/San Joaquin fever, desert rheumatism, valley bumps, Diagnosis • spherules (spores) in tissues or fluids • cultures of tissues or lesions • laboratory workers: infectious aerosols • increasing in California and Arizona – elderly population, droughts, HIV/AIDS Histoplasmosis • fungal infection of the respiratory system caused by Histoplasma capsulatum • AKA reticuloendothelial cytomycosis, cave disease, spelunker’s disease, Darling’s disease • highest incidence: Ohio, Missouri and Missippi Delta • found in bird droppings and bats • airborne spores enter ventilation systems • infected host asymptomatic, can become systemic and fatal (COPD) Candidiasis • bacterial microbiota (genitourinary tract and mouth) usually suppress infection • not affected by antibacterial drugs • changes in normal mucosal pH encourage growth (antibiotic therapy) • Readings question #1: What microorganisms cause candidiasis? How may this infection appear in infants? What is it called? • Color Plate 69 Cryptococcosis • Page 413 AKA fungal meningitis, cryptococcal meningitis due to Cryptococcus neoformans • spherical cells that reproduce by “budding” • have thick polysaccharide capsules • found in soil, pigeon roosts and nests • transmitted by inhalation of dried droppings • Figure 28 – 2 • usually subclinical unless “high risk” • if systemic: brain and meninges Brain Tissue with Cavities Aspergillosis • Readings question #2: What is the causative fungus? Where is it found? How is it spread? What are the symptoms for the disease? Pneumocystis Pneumonia (PCP) • Page 415 • caused by Pneumocystic carinii (P. jiroveci) found in healthy human lungs • high infection rate in general population but “high risk” have few or no symptoms • reside in lining of the alveoli • diagnosis: sputum samples (cysts from bronchoalveolar lavage) Readings Question #3 • How is the disease PCP spread? What are its symptoms? Is it potentially fatal? (If yes, how does death occur?)