23 - MYCOLOGY Fungal diseases may be discussed in a variety...

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Unformatted text preview: MYCOLOGY Fungal diseases may be discussed in a variety Fungal of ways. The most practical method for medical students is the clinical taxonomy which divides the fungi into: the Superficial mycoses Subcutaneous mycoses Systemic mycoses Opportunistic mycoses Principal tissue sites of deep mycoses in comparison to those of the superficial, cutaneous, and subcutaneous mycoses. SUPERFICIAL MYCOSES The superficial (cutaneous) mycoses are usually The confined to the outer layers of skin, hair, and nails, and do not invade living tissues. The fungi are called dermatophytes. Dermatophytes, or more properly, keratinophilic fungi, produce extracellular enzymes (keratinases) which are capable of hydrolyzing keratin.There are three genera of dermatophytes: keratin.There Malassezia furfur 秕秕秕秕秕秕 Trichophyton species (19 species) 秕秕秕 Trichophyton species Microsporum species 秕秕秕秕秕 Epidermophyton floccosum. 秕秕秕秕 Malassezia furfur 秕秕秕秕秕秕 Malassezia Malassezia furfur is a lipophilic “yeast” found Malassezia on skin flora. It can cause the following disorders: disorders: Pityriasis versicolor Fungemia in premature infant Trichophyton species 秕秕秕 species These infect skin, hair and nails. Rarely can cause subcutaneous infections, in immunocompromised individuals. Take 2-3 weeks to grow in culture. The conidia are large (macroconidia), smooth, thin-wall, septate (0-10 septa), and pencil-shaped; colonies a re a loose aerial mycelium which grow in a variety of colors. Identification requires special biochemical and morphological techniques (figure 10). Trichophyton rubrum is presently the most common cause of tinea in South Carolina. in Microsporum species ( 秕秕秕秕秕 ) Microsporum These may infect skin and hair, rarely nails. Its These prevalence has decreased significantly. When prevalent (15-20 years ago), this organism could be easily identified on the scalp because infected hairs fluoresce a bright green color when illuminated with a UV-emitting Wood's light. The loose, cottony mycelia produce macroconidia (figure 11) which are thickproduce walled, spindle-shaped, multicellular, and echinulate walled, (spiny). Microsporum canis is one of the most common dermatophyte species infecting humans. common Epidermophyton floccosum 秕秕秕秕 . Epidermophyton These infect skin and nails and rarely hair. They form yellow-colored, cottony cultures and are usually readily identified by the thick, bifurcated hyphae with multiple smooth, club-shaped macroconidia. multiple Fungi of subcutaneous infection Chromomycosis (caused by several Chromomycosis species of black molds; Fonsecaea edrosoi, Cladosporium carrionii, Phialophora verrua have been isolated most frequently). most Sporothrix schenckii Sporothrix schenckii 秕秕秕秕秕秕 SPOROTRICHOSIS is Primarily a disease of the cutaneous tissue and lymph nodes. Recently, pulmonary disease. SPOROTRICHOSIS Systemic mycoses Systemic Cryptococcus neoformans Cryptococcus Histoplasma capsulatum Coccidioides immites ( 厌厌厌厌厌厌厌 厌厌厌厌厌厌厌 Blastomyes dermatitides 厌厌厌厌厌厌厌 厌厌厌厌厌厌厌 Paracoccidiodes brasiliensis 厌厌厌厌厌厌厌厌 厌厌厌厌厌厌厌厌 Portals of entry of pathogenic and opportunistic fungi causing deep mycoses. Cryptococcus neoformans Oval , budding yeast surrounded by a wide polysaccharide capsule Cryptococcus neoformans Cryptococcus Cryptococcus neoformans Cryptococcus cryptococcosis No human to human transmission Infection follows inhalation of the cell of C. neoformans, which , in nature , are thought to be small , allowing the organism to enter deep into the lung. Histoplasmosis Histoplasmosis An intracellular mycoses of the reticuloendothelial system, attacking lungs, liver, spleen, bone marrow and occasionally kidneys, adrenals and intestines. COCCIDIOIDOMYCOSIS It may occur as either an acute, benign, self­limited disease or a chronic, malignant disseminated disease involving the cutaneous, subcutaneous, visceral or osseous tissue. Opportunistic Mycoses Opportunistic Candida 厌厌厌厌厌厌厌 Aspergillus 厌厌厌厌 Aspergillus 厌厌厌厌 Mucor 厌厌厌厌 Pneumocystis carinii( 厌厌厌厌厌厌 厌厌厌厌厌厌 Candida albicans Candida Aspergillus fumigatus; Aspergillus niger; Aspergillus Aspergillus flavus Allergic - hypersensitivity to the organism. Allergic Aggressive tissue invasion. Primarily a pulmonary Aggressive disease, but the aspergilli may disseminate to any organ. They may cause endocarditis, osteomyelitis, otomycosis and cutaneous lesions. and Fungus ball which is characteristically seen in the old Fungus cavities of TB patients. This is easily recognized by x-ray, because the lesion (actually a colony of mold growing in the cavity) is shaped like a half-moon (semi-lunar growth). The patients may cough up the fungus elements because the organism frequently invades the bronchus. Chains of conidia can sometimes be seen in the sputum. conidia ...
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