1. 1. Mycology and Fungal Pathogens
2. 2. Mycology Study of fungi Greater than 100,000 fungal species Only ~200 human/animal pathogen FUNGI Eukaryotes: Yeasts and molds Cell wall Chitin Cell membrane - ergosterol Chemoheterotrophs Require organic compounds for carbon and energy Food industry: bread, alcohol, edible fungi (mushrooms), cheeses Some are deadly Adapted to environments hostile to bacteria pH 5 High osmotic pressure Low moisture Complex carbohydrates (ex. Lignin from wood) Less nitrogen
3. 3. Yeast Unicellular fungi Spherical Facultative anaerobe Reproduce budding or fission Budding Yeast Ex. Saccharomyces Uneven division Bud forms on outer surface Parent nucleus divides One nucleus migrates into bud Cell wall forms, bud breaks away Fission Yeast Ex. Shizosaccharomyces Binary fission identical daughter cells
4. 4. Molds and Fleshy Fungi Multicellular Aerobic Composed of hyphae Long filaments of cells joined together Grow by elongating at ends Fragments break off to form new hyphae Hyphae: Vegetative Part that absorbs nutrients Aerial Projects above medium Bears reproductive spores
5. 5. Fungal Reproduction Molds (multicellular fungi) Asexual reproduction Fragmentation Hyphae break off to form new molds Spores Asexual spores Form by mitosis, detach from parent, germinate to form new hyphae identical to parent Sexual reproduction Sexual spores Formed by fusion of nuclei from two opposing mating strains Detach from parent structure Germinate into new mold Contain genes from both parent fungi
6. 6. Asexual Spores Examination of spores aid clinical identification of fungal infection Two Types Sporanigospore Formed in sac (sporangium) at end of aerial hyphae (sporangiophore) Ex. Rhizopus Hundreds of spores in a single sac
7. 7. Asexual Spores: Condiospore Also called Conidia (dust: detach easily and float like dust!) Not enclosed in a sac Seen as chains at end of conidiophore Ex. Aspergillus
8. 8. Other Conidia: Arthoconidia and Blastoconidia Arthoconidia = conidiospores formed by fragmentation of a hypha into single cells Ex) Coccidioides immitis Blastoconidia = conidiospores formed by buds coming off the parent cell Ex) yeasts like Candida albicans Other fungi: Cryptococcus (yeast stage)
9. 9. Spore Formation Hyphae forms conidia (or sporangia) Spores disseminate in air Inhalation irritants allergens also spores in respiratory system source of infection
10. 10. Fungal Toxins Some fungi secrete toxins Muscarin: Hallucinogenic Phalloidin: irreversible damage to liver cells Amanitin: inhibits RNA polymerase II activity Aflatoxin (Aspergillus flavus) Liver damage Ergot (Claviceps purpurea) Gangrene, convulsions, hallucinations (LSD) Deathcap (Amanita phalloides)
11. 11. Mycoses Fungal Infections Usually chronic, fungi grow slowly Treatment difficult Fungi are eukaryotes Antifungals can affect human cells Serious kidney, liver failure Types of Mycoses Cutaneous Subcutaneous Systemic Opportunistic
12. 12. Cutaneous Mycoses Fungal infection of skin, hair, nails Dermatophytes Cause only cutaneous infections Secrete keratinase to degrade keratin Trichophyton, Epidermophyton, Microsporum Need to remember those names and what they cause
13. 13. Tinea pedis: Athletes Foot Caused by Trichophyton Multicellular hyphae with asexual spores (arthroconidia) Results in scaling, flaking, itching of feet Transmission Contagious can be spread through contact Reservoirs = warm, damp areas Prevention Keep skin clean and dry Wear sandals in community pools and showers Wash hands after touching other people/ animals that may carry fungal infections Treatment Topical antifungals Trichophyton rubrum Do not need to remember treatments unless told
14. 14. Tinea capitis (ringworm of scalp) Caused by Microsporum genus Grows as multicellular hyphae asexual spores (conidiospores) Found in soil and on animals Results in inflammation, scarring, permanent hair loss Transmission = touching infected human or animal, touching infected objects Treatment = terbinafine hydrochloride (lamisil) ingestion
15. 15. Subcutaneous Mycoses Infection beneath the skin More dangerous than cutaneous Usually from soil dwellers invading puncture wounds Ex) Sporotrichosis: Sporothrix schenkii Most common subcutaneous mycosis Dimorphic: 25oC hyphae, spores 37oC yeastlike, budding Transmission = handling of soil or plant material Symptoms = small ulcer where it entered Spread along lymph vessels creating more ulcers Treatment = potassium iodide (ingestion), itraconazole
16. 16. Systemic Mycoses Fungal infection affecting internal organs Soil dwelling fungi Initiated by inhaling spores Infection in lungs Spreads to other parts of body Histoplasmosis: Histoplasma capsulatum Dimorphic = filamentous in soil, yeast-like morphology in tissue lives, multiplies in macrophages Symptoms: mainly mild respiratory infection Treatment: if severe, intravenous Itraconazole
17. 17. Histoplasmosis: geographic distribution Areas of moist soils are good for H. capsulatum growth more airborne spores
18. 18. Systemic mycoses: Coccidioidomycosis Valley Fever Coccidiodes immitis Dry, alkaline soils of American SW, S. America and Mexico Dimorphic = filamentous in soil; thick-walled spherule filled with spores in tissue Symptoms = Chest pain, fever, coughing, weight loss Diagnosis = Identification of spherules in tissue/fluids Treatment = Most recover without treatment
19. 19. Systemic Opportunistic Mycoses Opportunistic mycoses Fungal infection occuring in immunocompromised human/animal Ex) Pneumocystis pneumonia Pneumocystis jirovecii Few or no symptoms in healthy lungs Symptoms in immune compromised Primary indicator of AIDS Symptoms = fever, cough, difficulty breathing Diagnosis = detection of cysts in lung tissue/fluid Treatment = trimethoprimsulfamethoxazole
20. 20. Systemic opportunistic mycoses Ex) Aspergillosis Aspergillus fumigatus Transmission = airborne spores from soil and compost Most people inhale Aspergillus spores every day Destroyed by healthy immune systems Pathogenesis = germinate into hyphae in alveoli lesions Symptoms = fever, bloody cough, chest pain Diagnosis = lung tissue biopsy Treatment = amphotericin B, voriconizole
21. 21. FUNGAL PNEUMONIA Ascomycota Sac Fungus Aspergillus Organism: Aspergillus fungus Frequently found in compost heaps, air vents, pillows and airborne dust. Transmission: Inhalation of spores is primary cause of Aspergillosis. Course: Usually affects open spaces such as cavities that have formed in the lungs from preexisting lung diseases. Shows up as a tangled mass of fungus fibers, blood clots, and white blood cells. Fungus ball gradually enlarges, destroying lung tissue, but usually doesnt spread. Less often can become very aggressive and rapidly spread throughout the lungs and often through the bloodstream to the brain and kidneys (immune compromised). Diseases of the Respiratory System
22. 22. Opportunistic Normal Flora Candida albicans Part of normal flora of mouth, skin, intestine and vagina Opportunistic candidiasis - Oral thrush: whitish velvety sores of the mouth and tongue - Vaginitis (yeast infection) Candida blastoconidia (asexual spores) SEM Oral thrush in an infant
23. 23. Include Blastomycoses