Green Algal Infection in a Human

Abstract

Infection by unicellular green algae has not been described in humans. A case is reported in a 30-year-old woman who developed persistent infection of a healing operative wound on the dorsum of the right foot, after possible contamination by river water while canoeing. The wound was debrided 2 months later. Histologically, infected tissues contained mixed suppurative and granulomatous inflammation associated with endosporulating, round to oval microorganisms, ranging from 6-9 microns in diameter. Many of these organisms contained multiple, strongly periodic acid-Schiff, Gomori methenamine-silver, and Gridley fungus-positive granules in the cytoplasm. The organisms in tissue did not stain with fluorescent antibody conjugates specific for the two known pathogenic Prototheca species. In some organisms, electron microscopy revealed membranous cytoplasmic profiles considered to be remnants of degenerated chloroplasts. These findings are consistent with the presence of a green algal infection.

Human Protothecosis

“…It is believed that Prototheca species may infect humans through contact with potential sources or by traumatic inoculation with the algae (28,45,59,75,80). Systemic and local predisposing factors can be identified in nearly all patients.…”

“…Infection may also occur by penetration of the agent when a skin injury comes in contact with contaminated water (45,59,161). Prototheca spp.…”

Unusual Fungal and Pseudofungal Infections of Humans

“…In contrast to Prototheca, another alga that causes human infection (Table 1), Chlorella contains chloroplasts that give the lesions of chlorellosis a distinct green color (34,63,81). A single human infection has been reported thus far (41).…”

“…The single human case of chlorellosis took place in Nebraska and resulted from exposure of a surgical wound to river water (41). The wound drained a greenish-yellow exudate, and infected tissues contained endosporulating organisms ranging from 6 to 9 m in diameter.…”

“…Treatment of the only human case of chlorellosis consisted of debridement, irrigation, and gauze packing and removal to ensure drainage and granulation (41). Medical treatment with amphotericin B plus tetracycline has proven efficacious in the treatment of protothecosis and may be useful for chlorellosis should surgical excision prove inadequate.…”