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Unknown 5 = Uncinocarpus reesii
Culture: Cultures on Sabouraud's dextrose agar showed a suede-like to downy, greyish white colony with a tan to brown reverse.
Microscopy: Microscopic morphology showing typical single-celled, hyaline, rectangular to barrel-shaped, alternate arthroconidia, separated from each other by a disjunctor cell.
As both the culture and microscopic features closely resembled Coccidioides immitis an exoantigen test was done.
Exoantigen test: showing a positive result for Coccidioides immitis.
Comment: Based on the above culture, microscopy and exoantigen results an initial identification of Coccidioides immitis was made. However as the patient had no travel history to an endemic area a molecular identification using PCR amplification and sequencing of rDNA was performed which showed >98% homology to Uncinocarpus reesii.
Uncinocarpus reesii is a non-pathogenic, environmental saprophyte and is the closest known relative of Coccidioides immitis. It is often used as a surrogate organism for laboratory training in the USA. However its cross reactivity with the exoantigen test has not been previously reported.
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