Etiology Blastomyces dermatitidis and Blastomyces gilchristii belong to a group of fungi that exhibit thermal dimorphism. In the soil (22-25°C [71.6-77°F]), these fungi grow as mold and produce spores, which are the infectious particles. Following soil disruption, aerosolized mycelial fragments…
Etiology Histoplasmosis is caused by Histoplasma capsulatum, a dimorphic fungus found in the environment as a saprobe in the mycelial (mold) form and in tissues in the parasitic form as yeast. Epidemiology Two varieties of Histoplasma cause human histoplasmosis. The…
The aspergilli are ubiquitous fungi whose normal ecological niche is that of a soil saprophyte that recycles carbon and nitrogen. The genus Aspergillus contains approximately 250 species, but most human disease is caused by Aspergillus fumigatus , A. flavus ,…
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Etiology While more than 30 cryptococcal species have been described, 2 species ( Cryptococcus neoformans and C. gattii ) are responsible for the vast majority of disease. These species can be further classified by serologic and molecular typing techniques. Both…
Candidiasis encompasses many clinical syndromes that may be caused by several species of Candida . Invasive candidiasis ( Candida infections of the blood and other sterile body fluids) is a leading cause of infection-related mortality in hospitalized immunocompromised patients .…
Invasive fungal infections are a major cause of morbidity and mortality in the growing number of immunocompromised children. Fortunately, the therapeutic armamentarium for invasive fungal infections has markedly increased since the turn of the century ( Tables 260.1 and 260.2…
Q fever (for query fever, the name given following an outbreak of febrile illness in an abattoir in Queensland, Australia) is rarely reported in children but is probably underdiagnosed. Symptomatic patients can have acute or chronic disease. Etiology Although previously…
Etiology Ehrlichiosis in humans was 1st described in 1987, when clusters of bacteria confined within cytoplasmic vacuoles of circulating leukocytes (morulae), particularly mononuclear leukocytes, were detected in the peripheral blood of a patient with suspected Rocky Mountain spotted fever (RMSF).…
Members of the typhus group of rickettsiae (see Table 255.1 in Chapter 255 ) include Rickettsia typhi, the cause of murine typhus, and Rickettsia prowazekii, the cause of louse-borne or epidemic typhus. R. typhi is transmitted to humans by fleas,…