Medical Mycology Q&A Section A — MCQ Bank OmpathStudy

Medical Virology & Mycology — Complete Short Answer & Essay Q&A Compiled from past papers: BMM1301, MBMM 3300, MDBS3101 MBChB Year 3 --- --- MYCOLOGY --- SECTION B — SHORT ANSWER QUESTIONS --- Q: List four characteristics of systemic mycoses. A: 1. Caused by dimorphic fungi 2. Acquired primarily by inhalation of spores 3. Asymptomatic in immunocompetent individuals (subclinical infection common) 4. Can infect both healthy and immunocompromised hosts 5. Microscopy reveals granulomatous tissue reaction on biopsy --- Q: Describe the diagnosis of paracoccidioidomycosis. A: Microscopy: KOH wet mount of sputum, skin scrapings, or biopsy material reveals the pathognomonic "ship's wheel" or "Mickey Mouse" appearance — large yeast cells surrounded by multiple narrow-necked buds Culture: Growth on Sabouraud dextrose agar at 25°C (mold form) and 37°C (yeast form); requires conversion to confirm dimorphism Serology: Immunodiffusion and complement fixation tests detect specific antibodies (confirmatory) Histology: Granulomatous inflammation with giant cells containing the budding yeast forms --- Q: List four clinical manifestations of Cryptococcosis. A: 1. Meningitis / meningoencephalitis (most serious) — headache, fever, neck stiffness 2. Pneumonia — cough, chest pain, dyspnoea 3. Skin lesions — papules resembling molluscum contagiosum 4. Paralysis / focal neurological deficits in disseminated disease --- Q: List two fungi that multiply within macrophages. A: Histoplasma capsulatum Cryptococcus neoformans Aspergillus fumigatus --- Q: List two fungi that produce melanin. A: Paracoccidioides brasiliensis Wangiella (Exophiala) dermatitidis --- Q: List two fungi that affect the CNS. A: Cryptococcus neoformans Histoplasma capsulatum --- Q: List one fungus whose etiology is a basidiomycete. A: Cryptococcus neoformans (its teleomorph/sexual form is Filobasidiella neoformans , a basidiomycete; pigeon droppings are the environmental reservoir) --- Q: List two fungi that form yeast-like cells. A: Candida albicans Histoplasma capsulatum --- Q: List one similarity between 5-flucytosine and fluconazole. A: Both are antifungal agents (ergosterol biosynthesis pathway interference). More precisely, both are used to treat systemic fungal infections including cryptococcal meningitis, and both can penetrate the CNS. --- Q: List one similarity between Sporothrix schenckii and Blastomyces dermatitidis . A: Both are thermally dimorphic fungi (mold at 25°C, yeast at 37°C). Both also cause subcutaneous/deep mycoses in geographically defined endemic regions. --- Q: List one similarity between Epidermophyton and Microsporum . A: Both are dermatophytes that cause cutaneous mycoses (tinea infections), and both have many common commensal-related characteristics. --- Q: List one similarity between Clotrimazole and Miconazole. A: Both are azole antifungals that inhibit fungal ergosterol biosynthesis by blocking the cytochrome P450-dependent enzyme lanosterol 14-α-demethylase. --- Q: List one similarity between White Piedra and Paracoccidioidomycosis. A: Both are fungal infections; White Piedra is caused by Trichosporon spp. and Paracoccidioidomycosis by Paracoccidioides brasiliensis , but both can involve granulomatous or inflammatory tissue responses. --- Q: Name one fungus with the following characteristics: (a) Production of sclerotic bodies A: Phialophora verrucosa (agent of chromoblastomycosis) (b) Characterized by erythema nodosum A: Coccidioides immitis (coccidioidomycosis) (c) Associated with pigeon droppings A: Cryptococcus neoformans --- Q: Describe dimorphism in relation to systemic fungi. A: Dimorphic fungi exist in two distinct morphological forms depending on temperature and environment: At 25°C (environmental/room temperature): they grow as molds (filamentous, with hyphae and conidia) — the infective form At 37°C (human body temperature): they convert to yeast forms (or spherules in Coccidioides) — the pathogenic tissue form This conversion is triggered by temperature, CO₂ concentration, and nutritional factors. Examples include Histoplasma capsulatum , Blastomyces dermatitidis , Paracoccidioides brasiliensis , Sporothrix schenckii , and Coccidioides immitis . --- Q: Outline risk factors to fungal infections. A: 1. Immunosuppression — HIV/AIDS, corticosteroid therapy, malignancy (patients cannot mount an effective immune response against fungal spores) 2. Occupation — Farmers, construction workers, and archaeologists are exposed to fungal spores in soil 3. Obesity — The skin folds provide an excellent warm, moist environment for fungal growth 4. Poor hygiene — Fungal infections manifest more frequently in people with poor hygiene and superficial fungal disease risk 5. Indwelling catheters — In hospitals, these provide excellent routes for fungal etiological agents into the body --- Q: Explain any two virulence factors used by fungi to cause disease in the host. A: 1. Toxins: Fungi elaborate mycotoxins such as aflatoxins and ergot alka