Regarding human protothecosis, more than 200 cases of infection by Prototheca spp were reported in the literature [2]. Clinical manifestations include cutaneous forms (66%), olecranon bursitis (15%) and disseminated or systemic infections (19%) [2]. No direct human-to-human transmission has been reported, but infection through contact (such as by traumatic inoculation or insect bites) with the algae from potential sources have been reported [3, 4]. Possible sources of Prototheca spp include rural areas, trees, grass, soil, sewage, animals (cattle, deer, and dogs), animal droppings, foods (e.g., butter, potato skins, bananas, cow’s milk) [3].

Disseminated infection and those with risk factors such as immunosuppression or oncological patients are associated with higher mortality rates, a mortality of 56% has been reported [2]. In immunocompetent patients there are still no data, nevertheless there are certain occupations that are considered at higher risk of exposure to the pathogen such as farmers, workers of rice paddies and fishermen [2, 3]. In our case, it was impossible to know if the microorganism was acquired before or during the hospital stay. Nosocomial infections have been reported, though primarily associated following orthopedic or surgical procedures [3], even though our patient did not receive any invasive procedures when he developed symptoms during his hospitalization. But we considered he was colonized before, and heart failure decompensation favored the systemic manifestation symptoms.

Virulence factors for protothecosis are unknown. Our patient with history of diabetes (reported as a potential risk factor for protothecosis) developed severe algaemia with decompensated heart failure leading to a critical state in the ICU. It is suggested that the presence of comorbidities (e.g. cancer, diabetes, steroid use, AIDS, alcoholism, dialysis, surgery) is a risk factor that facilitates the infectious condition, although it is still unknown if they determine the severity of the infection [3].

Identifying Prototheca spp. often requires both microbiological and histopathological testing performed by trained personnel, as relying on only one method may result in misidentification for other similar-appearing fungal pathogens [2, 3]. For microbiology, this may involve using automated microbiological analyzes (blood cultures), with the help of Sabouraud dextrose agar, Candida spp chromogenic agar, biochemical carbohydrate assimilation tests, immunofluorescence, and molecular analyses [5]. For histopathology, tissue biopsies can be prepared with periodic acid-Schiff (PAS), Hematoxylin and Eosin or Grocott-Gomori methenamine silver (GMS) staining, which may show a characteristic morula with a thick wall and internal septations, with associated chronic granulomatous inflammation and infiltration of histiocytes, lymphocytes, and giant cells [5]. It is worth to highlight the need for diagnostic suspicion to aid in identification of the organism microbiologically.

To date there is no defined standard treatment for this infection, antifungals (e.g, amphotericin B, itraconazole, fluconazole, voriconazole) and antibacterials (e.g, tetracycline, gentamicin, amikacin) have been used with variable success rates [6,7,8,9,10,11]. In Colombia, 10 cases of protothecosis shown in Table 2 have been described, this being the first in critical condition with hematogenous dissemination. All reported patients had favorable outcomes despite not having a standardized treatment and receiving different management strategies. There are no data indicating whether there is a condition differentiated by sex, although to date it seems that in Colombia it is more frequent in men.