MKU MBMM 3300 Medical Mycology study guide with past exam questions & concise answers. Master fungal infections like Candidiasis & Histoplasmosis. Prep for succ
Medical Mycology — Study Guide Mount Kenya University MBMM 3300 School of Health Sciences This guide covers all examined topics in Medical Mycology as tested across MKU past papers and CATs from 2017/2018 to 2021/2022. Each section presents the exact exam question followed by concise point-form answers structured for quick revision. Questions on Histoplasmosis, Cryptococcosis, Candidiasis, and Mycetoma appear in nearly every sitting — prioritise these. Topics examined in both main papers and CATs carry the highest weight. Papers referenced: 2021/2022 2018/2019 2017/2018 Main Exams Medical Mycology CATs --- Topics Covered 1. True Pathogenic Fungi vs Opportunistic Fungi 2. Disease Name Matching 3. Risk Factors for Fungal Infections 4. Virulence Factors of Fungi 5. Eumycetoma vs Actinomycetoma 6. Histoplasmosis 7. Cryptococcosis 8. Dimorphism in Systemic Fungi 9. Paracoccidioidomycosis 10. Tinea Versicolor 11. Tinea Nigra Palmaris 12. Five Types of Dermatophytoses 13. Epidermophyton and Microsporum 14. Modes of Action of Antifungals 15. Candidiasis 16. Mycetoma 17. Systemic Mycoses — Laboratory Diagnosis 18. Characteristics of Systemic Mycoses 19. Classes of Fungi Based on Reproduction 20. Fungi with Special Characteristics --- 1. True Pathogenic Fungi vs Opportunistic Fungi Question: In what respect do mycoses caused by true pathogenic fungi differ from mycoses caused by fungi associated with opportunistic infections? What are the general consequences of these infections to the human host? - True pathogens infect healthy, immunocompetent individuals with normal host defenses - Opportunistic fungi only cause disease in immunocompromised hosts — HIV/AIDS, transplant recipients, diabetics, patients on steroids - True pathogens are geographically restricted e.g. Histoplasma capsulatum , Coccidioides immitis - Opportunistic fungi are ubiquitous in the environment e.g. Candida , Aspergillus , Cryptococcus - True pathogens have defined virulence mechanisms independent of host immune status - Consequences: chronic pulmonary disease, disseminated infection, CNS involvement, septicaemia, death in severe cases --- 2. Disease Name Matching Question: Match the common name of the disease with the clinical name - Darling's disease → Histoplasmosis - Valley fever → Coccidioidomycosis - South American / Brazilian Blastomycosis → Paracoccidioidomycosis - Mycotic Mycetoma → Pseudoallescheriasis - Balanitis → Candidiasis of the penis --- 3. Risk Factors for Fungal Infections Question: Outline risk factors to fungal infections - HIV/AIDS and other immunodeficiencies - Prolonged or broad-spectrum antibiotic use — disrupts normal protective flora - Corticosteroid or immunosuppressive therapy - Diabetes mellitus — impairs phagocyte function - Haematological malignancies e.g. leukaemia, lymphoma - Organ or bone marrow transplantation - Indwelling catheters and prosthetic devices - Extremes of age — neonates and elderly - Malnutrition and chronic illness --- 4. Virulence Factors of Fungi Question: Explain any two virulence factors used by fungi to cause diseases in the host 1. Capsule production — e.g. Cryptococcus neoformans - Polysaccharide capsule resists phagocytosis - Inhibits complement activation - Suppresses T-cell mediated immunity 2. Dimorphism - Switch between mould (environmental) and yeast (tissue) form - Yeast form resists host defenses and persists inside macrophages - e.g. Histoplasma , Blastomyces , Coccidioides Other virulence factors: - Melanin production — protects against oxidative killing by phagocytes - Enzyme secretion — proteases and lipases break down host tissue - Biofilm formation — protects Candida from antifungals and immune attack --- 5. Eumycetoma vs Actinomycetoma Question: Compare Eumycetoma and Actinomycetoma Feature Eumycetoma Actinomycetoma --- --- --- Causative agent True fungi e.g. Madurella mycetomatis Filamentous bacteria e.g. Nocardia , Actinomadura Grain colour Black or white White, yellow, or red Grain texture Hard, compact Soft, friable Treatment Antifungals — ketoconazole, voriconazole Antibiotics — TMP-SMX, streptomycin Response to treatment Poor Better response --- 6. Histoplasmosis Question: Discuss the causative agent, clinical manifestation and treatment of Histoplasmosis Causative agent: - Histoplasma capsulatum — thermally dimorphic fungus - Mould in environment, yeast in human tissue at 37°C - Found in soil enriched with bird and bat droppings - Endemic in Ohio and Mississippi River valleys; also found in parts of Africa Clinical manifestations: - Most infections (90%) are asymptomatic - Acute pulmonary histoplasmosis — flu-like illness, self-limiting, fever, cough, chest pain - Chronic pulmonary histoplasmosis — resembles TB, cavitation, fibrosis, haemoptysis - Disseminated histoplasmosis — fever, hepatosplenomegaly, pancytopenia, weight loss; common in immunocompromised - CNS involvement — meningitis in severe disseminated disease Treatment: - Mild to moderate: Itraconazole — drug of choice - Severe or disseminated: Amphotericin B first, then step down to itraconazole - Duration: 6–12 weeks minimum; longer in HIV patients - Lifelong suppressive therapy with itraconazole in AIDS patients --- 7. Cryptococcosis Question: Outline predisposing factors and diagnosis of Cryptococcosis. List four clinical manifestations of Cryptococcosis Predisposing factors: - HIV/AIDS — CD4 count below 100 cells/uL - Corticosteroid use - Organ transplantation - Haematological malignancies - Sarcoidosis Diagnosis: - India ink preparation — visualises capsule in CSF - Cryptococcal antigen test (latex agglutination) — highly sensitive and specific - Culture on Sabouraud dextrose agar — mucoid, cream-coloured colonies - Nigerseed/birdseed agar — brown colonies due to melanin production - Histopathology — mucicarmine stain highlights polysaccharide capsule Clinical manifestations: - Meningitis or meningoencephalitis — most serious - Pulmonary cryptococcosis — cough, chest pain - Skin lesions — umbilicated papules resembling molluscum contagiosum - Bone and joint involvement --- 8. Dimorphism in Systemic Fungi Question: Describe dimorphism in relation to systemic fungi - Dimorphic fungi exist in two morphological forms depending on temperature - At 25–30°C (environment/laboratory): grow as moulds with hyphae and conidia - At 35–37°C (human body): convert to yeast form - This thermal switching is a key virulence mechanism - Yeast form evades phagocytic killing and disseminates via bloodstream - Examples: Histoplasma capsulatum , Blastomyces dermatitidis , Coccidioides immitis , Sporothrix schenckii , Paracoccidioides brasiliensis --- 9. Paracoccidioidomycosis Question: Describe the diagnosis of paracoccidioidomycosis - Direct microscopy — sputum or tissue showing characteristic "pilot's wheel" / "mariner's wheel" yeast with multiple peripheral budding daughter cells — pathognomonic - Culture on Sabouraud agar — slow growing, mould form at 25°C; yeast at 37°C - Histopathology — GMS or PAS stain - Serology — immunodiffusion, complement fixation tests - Chest X-ray — bilateral butterfly infiltrates --- 10. Tinea Versicolor Question: Explain the clinical manifestation of Tinea versicolor - Caused by Malassezia furfur - Hypopigmented or hyperpigmented macules on trunk, neck, upper arms - More noticeable after sun exposure — affected areas fail to tan - Mild scaling, rarely itchy - Diagnosis by KOH prep — "spaghetti and meatballs" pattern (short hyphae + round spores) --- 11. Tinea Nigra Palmaris Question: Describe etiology and symptoms of Tinea nigra palmaris - Caused by Hortaea werneckii — a dematiaceous (black) fungus - Superficial infection of the palms, rarely soles - Presents as dark brown to black, non-scaly macule on palm - Painless and non-inflammatory - Can mimic malignant melanoma — important differential diagnosis - Common in tropical and subtropical regions, especially young females --- 12. Five Types of Dermatophytoses Question: Discuss five