An 85-year-old male presented with a fever lasting for 2 days. He had a history of adrenal insufficiency with prednisolone use for 2 years. Pruritic erythematous maculopapules on his lower extremities appeared 1 year ago. On examination, he was febrile, tachycardic, and tachypneic. Multiple erythematous plaques were accompanied by papules, shallow ulcers, and crusts on his four limbs (Figure 1). Empirical piperacillin/tazobactam therapy was initiated. Blood cultures obtained on admission were positive after 3 days of incubation. Gram stain revealed spherical Gram-positive organisms of various sizes (Figure 2). A subculture on a blood agar plate showed milky white yeast-like colonies (Figure 3). A lactophenol cotton blue wet mount preparation disclosed characteristic endosporulating sporangia (Figure 4). The organisms isolated from both blood and cutaneous wound cultures were identified as Prototheca wickerhamii using the API 20C identification system (bioMérieux, Marcy l’Etoile, France). Ketoconazole therapy was started on hospital Day 6. His clinical condition and cutaneous lesions improved with ketoconazole for a total of 4 weeks.

Multiple erythematous plaques are accompanied by papules, shallow ulcers, and crusts on his right upper limb and left lower limb.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082

Multiple erythematous plaques are accompanied by papules, shallow ulcers, and crusts on his right upper limb and left lower limb.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082
Multiple erythematous plaques are accompanied by papules, shallow ulcers, and crusts on his right upper limb and left lower limb.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082

Gram stain of blood culture reveals spherical Gram-positive organisms of various sizes resembling yeast. Magnification, × 1,000.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082

Gram stain of blood culture reveals spherical Gram-positive organisms of various sizes resembling yeast. Magnification, × 1,000.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082
Gram stain of blood culture reveals spherical Gram-positive organisms of various sizes resembling yeast. Magnification, × 1,000.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082

Milky white yeast-like colonies are observed on blood agar plate after incubation at 35°C for 3 days.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082

Milky white yeast-like colonies are observed on blood agar plate after incubation at 35°C for 3 days.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082
Milky white yeast-like colonies are observed on blood agar plate after incubation at 35°C for 3 days.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082

Wet-mount preparation with lactophenol cotton blue discloses spherical sporangia containing multiple endospores with symmetrical arrangement. Magnification, × 1,000.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082

Wet-mount preparation with lactophenol cotton blue discloses spherical sporangia containing multiple endospores with symmetrical arrangement. Magnification, × 1,000.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082
Wet-mount preparation with lactophenol cotton blue discloses spherical sporangia containing multiple endospores with symmetrical arrangement. Magnification, × 1,000.
Citation: The American Society of Tropical Medicine and Hygiene 91, 4; 10.4269/ajtmh.14-0082
Prototheca wickerhamii is an achlorophyllic alga and is ubiquitous in nature, which can cause human infections. The definite diagnosis usually depends on morphological identification of the organisms in wet slide preparations of cultures and/or direct identification in tissue specimens.1