Mucor amphibiorum / circinelloides / hiemalis / indicus / mucedo / racemosus / ramosissimus and Rhizopus azygosporus / homothalicus / microsporus / oligosporus / oryzae The species of mold represented in this assay are all members of a broad class of fungi known as zygomycetes. Zygomycetes are primitive but fast growing fungi. They are widely distributed in terrestrial environments, where they break down plant debris in soil. However, many species are common environmental contaminants that can cause food spoilage, and a few are pathogens of plants, insects and humans. By definition, all pathogenic zygomycotic species will grow at 37°C, with the possible exception of the M. circinelloides. The common genera that infect humans include Rhizopus, followed by Mucor, Rhizomucor, Absidia, Cunninghamella and Syncephalastrum. Underlying diseases in humans include cancer and leukemia, antibiotic or prednisone use, diabetes, deferoxamine and desferrioxamine therapy, transplantation, burn wounds and the associated forms of immunosuppressive therapies. The most common clinical form of zygomycosis is rhinocerebral disease followed by pulmonary, cutaneous/subcutaneous, gastrointestinal and disseminated disease. Mucor amphibiorum has not been reported in human infections. Mucor circinelloides has been reported as a rare cause of cutaneous infections in humans. Mucor hiemalis has been reported from a few cases of human cutaneous infection. Mucor indicus (synonym: M. rouxii) has been reported from human gastric and pulmonary infections, a case of necrotizing fasciitis and reports of hepatic infection in a bone marrow transplant recipient who had ingested contaminated medicine. Mucor racemosus has been infrequently reported as a causative agent of animal and human zygomycosis. Rhizopus microsporus accounts for 10-15% of reported human cases and has been implicated in cellulitis, cutaneous infection, zygomycosis, and gastrointestinal infections. However, rhinocerebral forms of R. microsporus are rare. Rhizopus oryzae (synonym: R. arrhizus) is the most common causative agent of zygomycosis, accounting for 60% of the reported culture positive cases and nearly 90 percent of the rhinocerebral form of infection.
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