Medically Important Fungi PDF

Medically important microorganism: fungi Dr Katrina Chung Pooi Yin Department of Microbiology  Learning outcomes ❖ Identify and describe the basic structures of fungi ❖ Explain the growth and reproduction of fungi ❖ Describe the common diseases in man caused by fungi Structure (1) ❖ Eukar...

Medically important microorganism: fungi Dr Katrina Chung Pooi Yin Department of Microbiology  Learning outcomes ❖ Identify and describe the basic structures of fungi ❖ Explain the growth and reproduction of fungi ❖ Describe the common diseases in man caused by fungi Structure (1) ❖ Eukaryotic with typical cellular Anatomy of yeast cell organelles - rigid cell wall: mannan, glucan and chitin - ergosterol as the major membrane sterol Growth ❖ Biphasic - yeast form - filamentous form ❖ Pathogenic fungi can take both forms YEAST Unicellular budding of yeast ❖ Round to oval ❖ May have capsule Pseudomycelium: ❖ May be pseudohyphae tubular, thread-like ❖ Dimorphic structure of yeast cells Filamentous fungi Hypha (hyphae) ❖ Vegetative (“underground”) - penetrate the supporting medium Aerial mycelium spores which is very and absorb nutrients distinct for each genus ❖ Aerial - normally for asexual reproduction Mycelium ❖ Tangled mass of hyphae Coenocytic vs septate hyphae  Reproduction Asexual (budding or sporulation) Sexual ❖ Spore produced by mitosis ❖ Spores that are formed by ❖ Vegetative spores fusion of cells and meiosis - blastospores, arthrospores, ❖ Four types of sexual spores chlamydospores - oospore, ascospore, ❖ Aerial spores zygospore, basidiospore - conidiospores, microconidia (C), macroconidia (A), sporangiospores (B) Mycelium Superficial mycoses (Dermatophytoses) ❖ Monomorphic, filamentous Clinical syndrome: Tinea fungi ❖ Microsporum spp - infect skin and hair ❖ Trichophyton spp - infect skin, hair and nails ❖Epidermophyton spp Scalp: Tinea capitis Trunk: Tinea corporis - infect skin and nails Infection of the nail bed: Tinea unguium (onychomycoses) Jock itch: Tinea cruris Sub-cutaneous mycoses (Eumycotic mycetoma) Sporothrix schenckii S. schenckii ❖ Clinical syndrome - Rose gardener disease - Pulmonary sporotricosis Rose gardener disease Systemic mycoses ❖ Originate primarily in the lung and may spread to many organ systems ❖ Transmitted via inhalation of spores produced by the fungi Fungi Clinical syndrome Blastomycosis Acute or chronic pulmonary: productive cough, chest pain, Blastomyces dermatitidis fever Skin lesions Histoplasmosis: fungus flu Histoplasma capsulatum Acute or chronic pulmonary Mediastinal lymphadenopathy Coccidioidomycosis Coccidiodes immitis Acute or chronic pulmonary Erythema nodosum Paracoccidioides Paracoccidioidomycosis brasiliensis Chronic mucocutaneous or cutaneous ulcers Opportunistic mycoses (1) Patients with compromised host defences are susceptible to ubiquitous fungi ❖ Cryptococcus neoformans ❖ Aspergillus fumigatus ❖ Candida albicans India ink preparation of ❖ Pneumocystis jirovecii Cryptococcis neoformans Gram stain of Candida albicans Giemsa stain of P jirovecii Aspergillus hyphae  Opportunistic mycoses (2) Fungi Clinical syndrome Meningitis Cryptococcus neoformans Atypical pneumonia Allergic aspergillosis Invasive aspergillosis in severely immunocompromised Candida albicans: Aspergillus fumigatus individuals Thrush Aspergilloma Thrush: prolonged antibiotic use, immunocompromised individuals Candida albicans Septicemia: immunocompromised, cancer patients Endocarditis: IV drug users Vaginitis: diabetic women Atypical pneumonia in premature infants and AIDS Candidiasis in toe-webs Pneumocystis jirovecii patients (inter-digital space) AMBOSS link General mycology https://next.amboss.com/us/article/KM0Upg Case study Question 1 to 3 A child presented to his physician with a circular dry scaly lesion with slightly elevated margins on the upper arm for the duration of one month. Pictures (A) and (B) of the KOH mount of skin scrapings from the lesion is shown. Quiz Question 1 What is the MOST likely diagnosis for this child? A. Tinea corporis B. Tinea capitis C. Tinea pedis D. Tinea unguium Quiz Question 2 The fungus that has MOST likely cause the infection in this child is Candida albicans. True False Quiz Question 3 What is the structure that is shown by the arrow in picture (A)? A. Microconidia B. Hyphae C. Spores D. Buds Quiz Question 4 Cryptococcus neoformans could cause brain infections in an immunocompromised patient. True False Quiz Question 5 Which site is usually infected by Sporothrix schenckii? A. Lungs B. Skin C. Bones D. Brain