Immunohistopathology of Prototheca wickerhamii in cutaneous lesions of protothecosis

Protothecosis is a rare infection caused by pathogenic algae of the genus Prototheca. Prototheca wickerhamii causes cutaneous/subcutaneous opportunistic infections in humans and small animals. The diagnosis of protothecosis is based on histopathological examination of this organism, which can be confused with other fungi and inflammatory cells in infected tissues. In this study, immunohistopathological investigation was made of infected cutaneous human and animal tissues exhibiting protothecosis using rabbit antiserum against P. wickerhamii. Serum detected P. wickerhamii in human and feline protothecosis tissues, and did not react with Candida albicans in the human kidney tissues showing candidiasis. This antiserum can therefore differentiate P. wickerhamii cells from the yeast-like cells of C. albicans and Prototheca zopfii in target tissues.