Medical Mycology Lecture 3 PDF

Medical Mycology 1  Mycology * Def: Science that studies fungi * Fungi: Eukaryotic heterotrophic Mos; may be saprophytic or parasitic Unicellular (Yeast) Multicellular (Filamentous)...

Medical Mycology 1  Mycology * Def: Science that studies fungi * Fungi: Eukaryotic heterotrophic Mos; may be saprophytic or parasitic Unicellular (Yeast) Multicellular (Filamentous) Dimorphic Oval, spherical or elongated Branched hyphae can form spores Yeast & hyphae forms Mycoses A- Cutaneous B- Subcutaneous C- Systemic (deep) - Limited to epidermis - Penetrates beneath skin - Deep within body or disseminated to internal organs Apple-green fluorescence Dermatophytes * Include 3 genera: Trichophyton, Epidermophyton & Microsporum * Infection site: keratinized tissues (nail, hair & skin); keratin as nutrition source * Disease: ringworm or tinea Target Class (drug) * Transmission: by infected skin scales Cell wall Echinocandins Polyenes (Amphotericin B , Nystatin) * Diagnosis: - Culture: on SDA & microscopy Cell - UV lamp (Wood's lamp examination): fluorescence Azoles (Fluconazole) membrane - Skin test: Ag-Ab reaction Allylamines (Terbinafine) DNA/RNA Fluorinated pyrimidines (Flucytosine) * Treatment: - Removal of infected & dead tissue Mitosis Griseofulvin - Antifungal: Topical (miconazole or clotrimazole) or oral (griseofulvin & itraconazole) 2/8  I. Cutaneous mycoses Name Site/Symptoms - Itching, blisters, rupture, discharge of fluids T. pedis (Athlete’s foot) - Skin fissures can lead to 2ry bacterial infections - Non-hairy skin: ring-like lesions T. corporis (body ringworm) scaly center inflamed periphery T. cruris (groin ringworm) - Can spread from upper thighs to genitals T. capitis (scalp ringworm) - Scalp: redness, edema, scaling, vesicle formation T. versicolor - Neck, trunk & arms: brownish red scaling - Nail: deformed, discolored & brittle T. ungium - Terbinafine (drug of choice) T. barbae Beard regions (face & neck) 3/8  II. Subcutaneous Mycoses 1- Sporotrichosis 2- Mycetoma *Causative Sporothrix schenckii Madurella grisea & Actinomadura madurae agent * Morphology Transmission: - Morphology: Dimorphic & Transmission Through traumatic lacerations or wounds - At 25°C: Thin, septate, twisted hyphae - At 37°C: as yeast, buds appear * Pathogenesis - Lesion: ulcerate , pus filled, spread to - localized abscess -> discharges pus, serum & blood & Diagnosis lymphatics, may be chronic - May lead to bone deformities - Microscopy: budding yeast or pseudohyphae - Defining characteristic: presence of colored grains - Culture on SDA: 25°C (hyphae), at 37°C (yeast) composed of compacted hyphae in exudate * Treatment - Oral itraconazole (drug of choice) - Surgical excision 4/8  III. Systemic mycoses - Pathogens; A- True: infect healthy individuals B- Opportunistic: infect immunocompromised - Dimorphic fungi: exhibit both yeast & mycelial forms 1- Coccidiomycosis 2- Histoplasmosis *Causative agent Coccidioides immitis Histoplasma capsulatum * Transmission - Inhalation of arthrospores - Inhalation of conidia * Pathogenesis - Airborne arthrospores enter lungs & - Airborne conidia enter lungs & germinate germinate - Pulmonary infections: - Can spread to bones & CNS ----> A- Acute but self-limiting meningitis B- Chronic, progressive & fatal - Dissemination is rare ---> invasion of cells of reticuloendothelial system (only fungus that exhibit intracellular parasitism). * Diagnosis Morphologic identification Exo-antigen test: Ags detected by immunodiffusion assay. DNA hybridization: measures degree of genetic similarity between DNA sequences. * Treatment - Amphotericin B & flucytosine - Ketoconazole, fluconazole, itraconazole 5/8  IV. Opportunistic Mycoses * Susceptible patients: diabetic, AIDS, cancer, taking immunosuppressive drugs, long use of broad spectrum ABs - N.B: competing bacterial flora are eliminated by antibacterial ABs, allowing yeast to overgrow 1- Candidiasis * Causative agent: Candida albicans * Diseases: 1- Oral candidiasis 2- Vaginal candidiasis 3- Cutaneous candidiasis 4- Systemic candidiasis (Mouth thrush) Symptoms - Raised, white - Itching, burning pain - Hand infections due to - Life-threatening. plaques on oral vulva & vagina. long immersion in water mucosa, tongue, - Thick or thin white - May involve GIT, or gums discharge - In moist warm skin; red, kidneys, liver & spleen. vesicular. - skin around nails: swollen, red & painful * Diagnosis - Gram- staining: oval cells, germ tubes & hypha - Culture on SDA: creamy colonies * Treatment - Topically: Nystatin or clotrimazole - Orally: ketoconazole, fluconazole & itraconazole * Germ tube: Tube-like outgrowth produced by germinating cells -----> develops into hypha. ** Pseudohypha: Chain of yeast cells; result of budding -----> forming hypha-like filament 6/8  2- Cryptococcosis 3- Aspergillosis *Causative agent Cryptococcus neoformans Aspergillus fumigatus * Transmission - Inhalation of spores * Pathogenesis - Occur in immunosuppression - Non-invasive (Aspergilloma) or Acute aspergillosis - Infections in lungs, can transmits to - Acute aspergillosis: most severe, fatal, infection of other organs e.g. CNS --> meningitis lung --> disseminated to brain, GIT & organs Mucoid, glistering colonies * Diagnosis A- microscopically: - Specimen: - Sputum shows septate branched hyphae - Specimens: (spinal fluid, sputum or (V-shaped branches); septate hyphae that branch at a skin lesion) --> stained e India ink ---- 45-degree angle. > encapsulated yeast - Tissue sections or biopsy: B- Serology:1- Agglutination test shows fungus ball 2- IF: detects Ag in tissue - Serology - PCR * Treatment Amphotericin B & flucytosine 1- Amphotericin B 2- Surgical removal of fungal masses or infected tissue 7/8 Thanks 8