Systemic mycoses

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Information about Systemic mycoses

Published on March 9, 2014

Author: Raghunathreddy


Systemic Mycoses : Systemic Mycoses Dr. Pendru Raghunath Reddy Slide 2: General characters Caused by mostly saprophytic fungi The fungi causing systemic mycoses are thermally dimorphic Contracted by inhalation of fungal elements in dust Infection starts as respiratory disease and if not cured, they disseminate to other body sites like bone, subcutaneous tissues, central nervous system, bone marrow…etc Common in north America and to a lesser extend South America not common in other part of the world Slide 3: Causative agents Histoplasma capsulatum Blastomyces dermatitidis Coocidioides immitis Paracoccidioides brasiliensis Slide 4: Histoplasmosis This is an intracellular infection of the reticuloendothelial system (RES) Starts as respiratory infection could be self –limiting Distribution The disease occurs world wide; however, it is most common in the USA In endemic areas the fungus is present in the soil, rotting trees and is particularly abundant in bird feces Slide 5: Causative agent Histoplasma capsulatum is now differentiated into two varieties 1. H. capsulatum var capsulatum which causes the classical, ubiquitous form of histoplasmosis 2. H. capsulatum var duboisii which causes African histoplasmosis Slide 6: Pathogenesis and clinical features Infection is acquired by inhalation Most infections of classical histoplasmosis are asymptomatic Some infected individuals develop pulmonary disease which resembles tuberculosis Disseminated histoplasmosis develops only in a minority of infected individuals Infection of the reticuloendothelial system manifests as lymphadenopathy, hepatosplenomegaly, fever and anemia with high rate of fatality Slide 7: Granulomatous and ulcerative lesions may develop on the skin and mucus membranes African histoplasmosis involves mainly the skin, subcutaneous tissues and bones The lungs are not commonly affected and disseminated disease is infrequent Slide 8: Laboratory diagnosis Microscopy Microscopic examination of stained smears of blood, bone marrow, scrapings from lesions or biopsies of lymph nodes In classical histoplasmosis, small intra and extra cellular yeast cells are seen in Giemsa or wright stained smears In African histoplasmosis, large, thick walled yeast cells and pronounced giant cell formation are noted in infected tissue Slide 9: Culture Specimen is inoculated onto SDA and glucose cysteine blood -agar and incubated at room temperature and 370C, respectively At room temperature, white, cottony, mycelial growth appears, with large (8-20 µm) thick-walled, spherical spores with tubercles (finger-like projections) Slide 11: Serology Antibodies can be detected by serological tests such as latex agglutination, CFT, precipitation tests Skin test Delayed hypersensitivity develops following infection It can be demonstrated by skin testing with ‘histoplasmin’ which is analogus to the tuberculin test for tuberculosis In histoplasmosis, skin tests are more specific than serological methods Slide 13: Blastomycosis This is a chronic infection, characterised by the formation of suppurative and granulomatous lesions in any part of the body but with a marked predilection for the lungs and skin Distribution Infection is largely confined to the North American continent In recent years, several cases have been reported from India Slide 14: Causative agent: Caused by thermally dimorphic fungus Blastomyces dermatitidis Pathogenesis and clinical features Source of infection: Soil Mode of infection: Inhalation Primary infection of the lungs may resemble tuberculosis or histoplasmosis The fungus may spread from the lungs through the bloodstream and form multiple abscesses in various parts of the body Slide 15: Cutaneous disease usually affects the skin of the face or other exposed parts of the body The initial lesion is papule, around which secondary nodules develop and coalesce, leading to large, elevated ulcerative lesions Slide 16: Blastomycosis Slide 17: Blastomycosis Slide 18: Laboratory diagnosis Specimens Sputum, pus, exudates, urine and biopsies from lesions Microscopic examination In tissues and in culture at 370C, the fungus appears as a budding yeast cell, which is large (7-20 µm) and spherical, with a thick, double-contoured wall Each cell carries only a single broad-based bud Slide 19: Culture At room temperature, the culture is filamentous with septate hyphae and many round or oval conidia, and in older cultures chlamydospores also occur Slide 21: Coccidioidomycosis It may occur as either an acute, benign, self-limited lung infection or a chronic, malignant disseminated disease involving the cutaneous, subcutaneous, visceral or osseous tissue Distribution The disease is endemic in the dry, arid regions of south -western USA, where the fungus is present in the soil and in rodents Causative agent: Caused by the thermally dimorphic fungus Coccidioides immitis Slide 22: Pathogenesis and clinical features Infection is acquired by inhalation of dust containing arthrospores of the fungus In most cases, the respiratory infection is asymptomatic and leads to lifetime immunity Many persons develop a self-limited influenza-like fever (known as ‘valley fever’, ‘San Joaquin Valley fever’ or ‘desert rheumatism’) Less than 1% of infected persons develop chronic progressive disseminated disease (coccidioidal granuloma) which is highly fatal. It resembles clinically and histologically disseminated tuberculosis Slide 23: SPHERULE ENDOSPORES ARTHROCONIDIA SOIL ANIMAL HUMAN ____________ Slide 24: Coccidioidomycosis Slide 25: Laboratory diagnosis Specimens Sputum, pus and biopsy material Microscopic examination Culture Specimens are inoculated on SDA medium and incubated at room temparature and 370C The spherule is 15-75 µm in diameter, with a thick doubly refractile wall and filled with endospores Slide 26: The mycelial phase consists of hyphae which fragment into arthrospores that are highly infectious Slide 27: Paracoccidioidomycosis This is a chronic granulomatous disease of the skin, mucosa, lymph nodes and internal organs Distribution As the disease is confined to South America, it is called South American blastomycosis Causative agent: Caused by the thermally dimorphic fungus Paracoccidioides brasiliensis Slide 28: Pathogenesis and clinical features The spores are inhaled and result in primary pulmonary infection that spreads by the hematogenous route to the mucosa of the nose, mouth, gastrointestinal tract, skin and lymphatics This leads to ulcerative granulomas of buccal and nasal mucosa, which are a prominent feature of the disease Slide 30: Laboratory diagnosis Specimens Sputum, pus, crusts and biopsies from granulomatous lesions Direct microscopy Reveals numerous yeast cells (10 – 60 µm) with multiple buds, which is diagnostic Mutiple buds attached to the mother cell (resembling ‘pilot wheel’) by very narrow necks are the hallmark of this fungus Slide 31: THE PILOT’S WHEEL Slide 32: Culture P. brasiliensis grows in the mycelial phase in culture at 25-300C and in the yeast phase in tissue or at 370C Blood agar and incubation at 370C is recommended for isolation of the yeast phase Mycelial phase of the fungus develops on SDA incubated at 25-300C Identification depends on conversion from the mycelial to the yeast phase Slide 34: Treatment for systemic mycoses Amphotericin B is the drug of choice for severe (invasive) disease Oral azoles (Ketoconazole, itraconazole, fluconazole) are used for less severe infections Corrective surgery may be used for pulmonary and cutaneous lesions

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