Lecture 13 & 14 Introduction to Medical Mycology PDF

Microbiology & Immunology Unit Lecture 13 & 14 Introduction to Medical Mycology (I& II) Dr. Rasha Mokhtar Elnagar M.B.B.C, MSc, PhD, MD Medical Microbiology and Immunology Associate Professor of Medical Microbiology & Immunology Consu...

Microbiology & Immunology Unit Lecture 13 & 14 Introduction to Medical Mycology (I& II) Dr. Rasha Mokhtar Elnagar M.B.B.C, MSc, PhD, MD Medical Microbiology and Immunology Associate Professor of Medical Microbiology & Immunology Consultant Microbiology & Immunology  Content of lecture  General properties and structure of Fungi  Morphology of Fungi  Classification of medically important fungi  Human mycosis  General Properties of Fungi Fungi are eukaryotic organisms having true nuclei and nuclear membrane. Structure of Fungi: Cell wall components (rigid): o Chitin: polymer of N-acetylglucosamine (NAG) sugar without amino acids. o β-D-Glucan. o Mannan as in Candida spp. o Galactomannan: in Aspergillus spp.. Cell membrane: Contains ergosterol. Cytoplasm: Contain the nucleus, ribosomes, mitochondria,.. Morphology of Fungi: 1- Moulds (Filamentous fungi):  Branching filaments or tubules which are called hyphae.  Hyphae may be septated or non-septated.  Mass of hyphae = mycelium  Examples:  Septated Mould: Aspergillus spp., Penicillium.  Non-septate Mould: Mucor. Non-septated Septated 2-Yeast:  Unicellular fungi (rounded or oval in shape).  Examples: Cryptococcus neoformans, Malassezia Candida.  Reproduce by budding.  In Candida the buds may separate from the mother cell or stay attached forming pseudohyphae. 3- Dimorphic fungi:  Grow as yeast during infection in the body & on incubating at 37°C.  And as moulds when inoculated at room temperature (25°C).  Examples: Histoplasma capsulatum  Classification of medically important Fungi I. Primary pathogenic fungi (endemic mycosis): Cause disease in immunocompetent individuals e.g. dimorphic fungi as Histoplasma capsulatum. II. Opportunistic fungi: Cause disease in immunocompromised individuals e.g. Candida.  Human mycosis Definition: Disease caused by fungi. Types of mycosis: 1. Superficial mycosis: Fungal infection that involve the outermost layers of the skin. Example: Pityriasis versicolor. Superficial skin infection with hypo/hyperpigmentation lesions. Caused by: Malassezia spp. which is a skin normal flora. 2. Cutaneous mycosis: Fungal infection which extend deeper into the dermis, hair and nail. Example: Dermatophytosis (Tinea). Fungal infection of (skin, hair and nails) caused by a group of keratinophilic filamentous fungi called Dermatophytes. Dermatophyte species include: Trichophyton, Microsporum, Epidermophyton. Mode of transmission: o Direct contact with infected human, animal, or soil. o Indirect contact (Sharing clothes, combs, hats, brushes and towels). Clinical lesions of Dermatophytosis: 1. Tinea capitis: It affects Hair and Scalp. 2- Tinea barbae: It involves beard and mustache area. 3. Tinea Corporis: It Affect non hairy, smooth skin. 4. Tinea pedis: (“Athlete’s foot”): It involves the toe web and the sole. 5- Tinea cruris: Lesion involves groin. 6. Tinea unguium:(Onychomycosis): Lesion involves nails. 3. Sub cutaneous mycosis: Fungal infection that involve the subcutaneous tissue, muscle and fascia e.g. (Mycetoma). 4. Systemic mycosis: Fungal infection that involve many organ systems. 5.Opportunistic Mycosis: Fungal infections in immunocompromised individuals caused by saprophytic fungi (e.g. Candida, Aspergillus, Mucor and Cryptococcus). A. Aspergillosis: Allergic, Pulmonary and Invasive Aspergillosis. B. Cryptococcosis: Present in pigeon dropping, common in HIV patients. C. Mucormycosis: common in diabetic patients. D. Candidiasis: (Candida albicans and non albicans) Can cause cutaneous, mucocutaneous and systemic infection. Oral candidiasis Vaginal candidiasis Cutaneous candidiasis UTI. Mycotoxicosis: Poisoning of man and animals due to ingestion of food contaminated by fungal toxins. Examples:  Aflatoxin: produced by Aspergillus flavus→ liver damage and hepatocellular carcinoma.  Ochratoxin: produced Aspergillus or Penicillium→ Kidney damage. Q1: Which of these is a component of the cell membrane of fungi? A. Cholesterol B. Chitin C. Ergosterol D. Peptidoglycan Q2: Tinea pedis or (“Athlete’s foot) means: A. Fungal infection of scalp B. Fungal infection of toe web C. Fungal infection of non-bearded parts of the face D. Suppurative bacterial infection of scalp