Introduction to Mycology and Dertmatophytes
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This document discusses the structure, growth, and types of medical mycoses (fungal infections). It notes that fungi have cell walls containing chitin and beta-glucan, and cell membranes containing ergosterol, which are targets of antifungal drugs. There are two main types of fungi - yeasts and molds. Medical mycoses are divided into cutaneous (skin), subcutaneous, systemic, and opportunistic categories. Common cutaneous mycoses include ringworm, athlete's foot, jock itch, and nail fungal infections caused by dermatophyte fungi. Candidiasis is caused by Candida species and can cause oral or vaginal infections when bacteria levels are
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Introduction to Mycology and Dertmatophytes
- 1. Mycology Aman Ullah B.Sc. MLT M. Phil Microbiology Master in Health Research Certificate in Health Professional Education
- 2. STRUCTURE & GROWTH • Fungi are eukaryotic organisms • Two fungal cell structures are important medically: • The fungal cell wall consists primarily of chitin • The fungal cell wall contains other polysaccharides as well, the most important of which is -glucan, a long polymer of D-glucose • it is the site of action of the antifungal drug • The fungal cell membrane contains ergosterol, also site of action of antifungal drug
- 3. STRUCTURE & GROWTH • There are two types of fungi: yeasts and molds • Yeasts grow as single cells that reproduce by asexual budding • Molds grow as long filaments (hyphae) and form a mat (mycelium) • Some hyphae form transverse walls (septate hyphae), whereas others do not (nonseptate hyphae) • Several medically important fungi are thermally dimorphic, i.e., they form different structures at different temperatures • They exist as molds in the environment at ambient temperature and as yeasts (or other structures) in human tissues at body temperature
- 4. STRUCTURE & GROWTH • Most fungi are obligate aerobes; some are facultative anaerobes; but none are obligate anaerobes • The natural habitat of most fungi is environment • An important exception is Candida albicans, which is part of the normal human flora
- 5. FUNGAL TOXINS & ALLERGIES • In addition to mycotic infections, there are two other kinds of fungal disease: • Mycotoxicoses, caused by ingested toxins, and • Allergies to fungal spores • The best-known mycotoxicosis occurs after eating Amanita mushroom • Allergies to fungal spores, particularly those of Aspergillus, are manifested primarily by an asthmatic reaction, eosinophilia
- 6. Mycosis • Infection caused by fungi is called mycosis • Medical mycoses can be divided into four categories: • Cutaneous • Subcutaneous • Systemic • Opportunistic
- 7. CUTANEOUS MYCOSES • Also called dermatophytoses • These common diseases are caused by a group of related fungi, the dermatophytes • Dermatophytes fall into three genera, each with many species: • Trichophyton • Epidermophyton • Microsporum
- 8. CUTANEOUS MYCOSES Transmission • Transmission from human to human or animal to human is by infected skin scales on inanimate objects • Only the pathogenic fungi are capable of human-to- human spread Pathology • A defining characteristic of the dermatophytes is their ability to use keratin as a source of nutrition • This ability allows them to infect ker-atinized tissues and structures, such as skin, hair, and nails
- 9. CUTANEOUS MYCOSES Clinical significance • Dermatophytoses are characterized by itching, scaling skin patches that can become inflamed • Specific diseases are usually identified according to affected tissue (for example, scalp, pubic area, or feet) • But a given disease can be caused by any one of several organisms, and some organisms can cause more than one disease
- 10. CUTANEOUS MYCOSES • Tinea pedis (“athlete’s foot”):The infected tissue is initially between the toes but can spread to the nails, which become yellow and brittle • Tinea corporis (“ringworm”): Although any site on the body can be affected, lesions most often occur on nonhairy areas of the trunk • Tinea capitis (“scalp ringworm”):Disease manifestations range from small, scaling patches, to involvement of the entire scalp with extensive hair loss • Tinea cruris (“jock itch”):Disease manifestations are similar to ringworm, except that lesions occur in the moist groin area, where they can spread from the upper thighs to the genitals • Tinea unguium (onychomycosis): Nails thicken and become discolored and brittle
- 11. Tinea pedis Tinea corporis Tinea capitis Tinea cruris Tinea unguium
- 12. Candidiasis (candidosis) • Candidiasis is caused by the yeast Candida albicans and other Candida species, which are normal body flora found in the skin, mouth, vagina, and intestines • Infections occur when competing bacterial flora are eliminated, for example, by antibacterial antibiotics, allowing the yeast to overgrow • Candida infections have various manifestations, depending on the site and the degree of immunoincompetence of the patient • For example, oral candidiasis (thrush) presents as raised, white plaques • on the oral mucosa, tongue, or gums • The plaques can become confluent and ulcerated and spread to the throat • Vaginal candidiasis presents as itching and burning pain of the vulva and vagina, accompanied by a white discharge • Systemic candidiasis is a potentially life-threatening infection that occurs in immunocopromised patient • Systemic candidiasis may involve the gastrointestinal (GI) tract, kidneys, liver, and spleen.