Prototheca may also be cultured on blood agar, heart-brain infusion agar and beef infusion broth. These features differentiate Prototheca from other types of algae. Protothecosis demonstrates rounded endospores, typically 6-10 microns in diameter, either extracellularly or within macrophages. They are best visualized with special stains used to highlight fungi, such as periodic acid-Schiff or Gomori methenamine silver stains. The diagnostic feature of Prototheca wickerhamii is the presence of sporangia with a central rounded endospore, surrounded by corona of molded endospores.
Surgical excision is the treatment of choice in all cases amenable to excision.
Protothecosis is notoriously difficult to eradicate pharmacologically. Due to the rarity of this disease, there is no defined pharmacologic protocol. There are also isolated reports of successful treatment of localized disease with ketoconazole. Sensitivity in vitro has not been shown to correlate with in vivo efficacy. The goals of pharmacotherapy are to reduce morbidity and prevent complications.