Experimental protothecosis in labortory animals

Protothecosis in human medicine

Prototheca spp. are ubiquitous achlorophyllous algae that produce disease in humans and animals. In the past years infections with Prototheca have obtained increasing importance in human medicine. The cases have been classified into three clinical forms: cutaneous and/or subcutaneous infection, synovitis of olecranon bursa or other fibrous tissue and systemic infection. Patients with a mild degree of immunosuppression may become colonized by Prototheca spp. with a subsequent worsening of their immune surveillance and spread of the disease. Among the numerous pharmacologic agents tried, amphotericin B is the most promising. Successful treatment of protothecosis involves radical excision of the involved structures.

Experimental cutaneous protothecosis in mice: epithelioid cell granuloma formation

Prototheca wickerhamii, isolated from skin biopsy specimens of a patient with cutaneous protothecosis, were cultured in Sabouraud's medium and inoculated in the skin of 8 ICR albino mice and 3 BALB/c mice. Only in 3 ICR albino mice and 3 BALB/c mice were organisms found in skin tissue, as confirmed by identification of organisms by staining with periodic acid-Schiff (PAS) stain and culture. Histologic findings from affected nodular skin lesions indicated epithelioid cell granuloma and histiocytic cell infiltrates in the dermis and subcutaneous tissue.

Ultrastructure of Prototheca zopfii in bovine granulomatous mastitis

Mammary glands from cows with protothecal mastitis were examined by light and electron microscopy at 6, 13, 20, and greater than 180 days after infection. With increasing time, there were increases in severity of granulomatous inflammation, number of endospores and sporangia, and ratio of degenerate to intact algae. Algae were found in macrophages but were not seen in neutrophils, epithelial cells, or myoepithelial cells. Macrophages containing algae were markedly enlarged, chiefly from reduplication of the Golgi complex and its associated vesicles. Intracellular algae were degenerate and consisted of intact cell wall profiles which contained membrane fragments but lacked nuclei and cytoplasmic organelles. Degenerate algae in vitro had thin cell walls and did not undergo internal lysis. Cell wall material of intracellular algae stained as an acidic, nonsulfated, carboxylated glycoprotein. These findings suggest that intracellular Prototheca zopfii degenerate by progressive lysis of internal organelles with persistence of cell wall glycans and that development of aberrant cell wall forms occurs as a defective response by host macrophages.

Metastatic protothecal retinitis in a dog. Electron microscopic observations

Disseminated protothecosis, due to Prototheca wickerhamii, was present in a two-year-old female dog with a nine-month history of hemorrhagic colitis and diarrhea. Shortly thereafter, the dog developed "acute blindness" of the left eye. Euthanasia was done after medical therapy failed to control the disease. Histologically, the eye had multiple microabscesses and necrotic foci containing myriad protothecal organisms under the detached retina. Numerous organisms also were present in the mucosa and walls of the colon. The identification of P. wickerhamii was confirmed by the histologic appearance and immunofluorescent studies. The ultrastructural features of P. wickerhamii also were studied.