Protothecosis, an algal infection: report of a case in man

Protothecosis

Protothecosis is a rare infection caused by achlorophyllic algae that are members of the genus Prototheca. They are ubiquitous in nature in organic material. The clinical manifestations can be acute or chronic and local or disseminated. The disease is classified as cutaneous, causing bursitis or disseminated/systemic, affecting both immunocompetent and immunosuppressed patients, with more severe and disseminated infections occurring in immunocompromised individuals. Prototheca wickerhamii and Prototheca zopfii are the most frequent organisms reported in humans. Diagnosis is made by observing asexual sporangia (thecas) on histopathological examination of tissue. Medical and surgical treatment should be considered. Ketoconazole, itraconazole, fluconazole, voriconazole, posaconazole, and amphotericin B are the most commonly used antifungals. Voriconazole and amphotericin B are highly effective against Prototheca spp. Treatment failure is not uncommon because of the comorbidities that limit the therapeutic outcome.

Prototheca wickerhamii infection of a corneal graft

Algae are generally noninfectious agents in mammals, with few known pathogenic algae. Prototheca is an achlorophylic nonphotosynthetic algae, globally ubiquitous, and readily isolated from rivers, lakes, ponds, and soil. Although canine and bovine protothecosis have been reported more widely, infections in humans are rare, particularly in patients with an intact immune system. The majority of protothecal infections in humans is associated with Prototheca wickerhamii. We report an unusual case of P. wickerhamii infection in an immunocompetent corneal transplant patient.

Human protothecosis

Human protothecosis is a rare infection caused by members of the genus Prototheca. Prototheca species are generally considered to be achlorophyllic algae and are ubiquitous in nature. The occurrence of protothecosis can be local or disseminated and acute or chronic, with the latter being more common. Diseases have been classified as (i) cutaneous lesions, (ii) olecranon bursitis, or (iii) disseminated or systemic manifestations. Infections can occur in both immunocompetent and immunosuppressed patients, although more severe and disseminated infections tend to occur in immunocompromised individuals. Prototheca wickerhamii and Prototheca zopfii have been associated with human disease. Usually, treatment involves medical and surgical approaches; treatment failure is not uncommon. Antifungals such as ketoconazole, itraconazole, fluconazole, and amphotericin B are the most commonly used drugs to date. Among them, amphotericin B displays the best activity against Prototheca spp. Diagnosis is largely made upon detection of characteristic structures observed on histopathologic examination of tissue.

Protothecosis in patients with cancer: case series and literature review

OBJECTIVE

To review our recent experience with protothecosis in patients with cancer at The University of Texas MD Anderson Cancer Center, and compare these cases with others reported in the literature.

METHODS

We report on three patients with protothecosis and cancer who were seen at The University of Texas MD Anderson Cancer Center from January 1979 to May 2002, and reviewed all cases of protothecosis in patients with cancer reported in the literature since 1966.

RESULTS

Overall, 13 cases of protothecosis complicating cancer were evaluated. The median age of the patients was 41 years (range, 7-73 years). Seven patients (54%) had an underlying hematologic malignancy, and one infection occurred after bone marrow transplantation. Neutropenia was uncommon in these patients (14%). Prototheca wickerhamii was the most common Prototheca species identified as the causative agent of infection. Skin infection was the most common presentation of protothecosis, occurring in five patients (38%), followed by disseminated disease in three patients (23%), algaemia in three patients (23%), pulmonary infection in one patient (8%), and olecranon bursitis in one patient (8%). Information on the use of antifungal therapy was available for ten patients. Seven of the ten patients received amphotericin B, while three received triazoles (fluconazole in two, itraconazole in one). Breakthrough protothecosis occurred during the administration of systemic antifungal therapy with itraconazole in one patient. All seven patients who received amphotericin B showed a response, as did one of the three patients given triazoles. Seven (58%) of the patients died during the study period, only one (17%) of protothecosis.

CONCLUSIONS

Protothecosis is an uncommon infection in cancer patients, implying that Prototheca spp. have a low pathogenic potential in this population. Pulmonary involvement in particular is uncommon in these patients. Amphotericin B appears to be the most effective antifungal agent; the role of triazoles in treating protothecosis is uncertain, but they may be less effective.

Protothecosis

Intravenous amphotericin B remains the most effective drug for eradicating Prototheca infections. It should be used as a first-line agent in cases of disseminated disease and in patients with severe underlying illness or with immunosuppression or immunocompromise. Azole antifungals and surgery should be reserved for patients with more localized disease. Itraconazole appears to be the most effective agent of this drug class, and it should be administered at 200 mg/day for 2 months. Surgical excision should be considered as a first-line therapy in patients who present with olecranon bursal infections.

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.

Bovine mastitis due to algae of the genus Prototheca

Protothecosis was described in many animals, with bovine mastitis being the main form. The increasing number of isolations of Prototheca spp. from bovine mastitis cases indicates the need of a detailed evaluation of this problem. Besides this, these algae do not respond to treatment with the antimicrobians most frequently applied, leading to elimination of the affected animals, as the best method to control the disease. In two dairy farms in the State of São Paulo, Brazil, a total of 155 lactating cows and 52 dry cows were examined. Milk samples were aseptically collected from lactating cows with clinical or subclinical mastitis. From dry cows, secretion samples from all quarters were collected. All samples were then taken to microbiological exams. At dairy farm 1, Prototheca spp. was isolated from 14.95% milk samples from lactating cows, (all of them cases of subclinical mastitis), and from 8.06% samples from dry cows. At dairy farm 2, Prototheca spp. was isolated from 5.1% milk samples and there were ten cases of clinical mastitis due to this agent. Although clinical mastitis has been considered the main form of occurrence of this pathology until now, it is important to consider Prototheca spp. as subclinical mastitis pathogen. Prototheca zopfii was the main specie isolated. In this study a high rate of intramammarian infections, as clinical or subclinical mastitis during lactation as well as in dry period, was observed, high lighting the importance of suitable diagnosis, so that control and preventive measures can be implemented to avoid dissemination of the agent.

Cutaneous manifestations of Prototheca infections

The genus Prototheca comprises several species, the most prevalent of which is Prototheca wickerhamii. These achlorophyllic algae are found in the slime flux of trees and in freshwater environs. Cutaneous infection with these microbes was first reported 30 years ago. Subsequent case reports have described other manifestations including systemic disease. Asymptomatic and stationary cutaneous plaques may be seen in otherwise healthy patients. Susceptibility to infection is ill defined but may involve an inability of neutrophils to effectively eradicate phagocytosed organisms. Characteristic morula are seen histologically. Antifungal medications are the most effective therapy.

Cutaneous protothecosis and AIDS

Cutaneous protothecosis is an uncommon algal infection with a varied clinical presentation that occurs mainly in immunocompromised patients. We describe a 33-year-old Hispanic woman with AIDS who had a verrucous plaque on the dorsum of her hand. A biopsy specimen revealed organisms suggestive of Prototheca. Culture confirmed the organism to be Prototheca wickerhamii. To our knowledge, this is the first case of cutaneous protothecosis reported in a patient with AIDS.

Protothecosis: a report of two cases in Japan and a review of the literature

Protothecosis is an emerging opportunistic infection caused by species belonging to the genus Prototheca. Two Japanese cases of protothecosis are documented with a critical review of the literature. A current perspective concerning the microbiology and disease entity of protothecosis is described in detail.

Simple new test for presumptive differentiation between genus Candida and genus Prototheca

A differential test was made between genus Candida and genus Prototheca using a new and very simple differential test. A total of 59 strains of Candida and 78 strains of Prototheca were used. The basis of the test was the differential use of a disc carrying 60 mcg of Ribostamycin to which all the Candida were resistant and the Prototheca inhibited.

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.

The effect of amphotericin B on the ultrastructure of Prototheca species

Prototheca zopfii and prototheca wickerhamii stains were exposed to subinhibitory concentrations of the antimycotic amphotericin B, and the effect of the treatment on their ultrastructure was assessed. The results revealed ultrastructural changes in the treated cells, expressed by swelling of mitochondria, degradation of cell organelles, accumulation of microbody like structures, lipid droplets and starch granules in the cytoplasm, and changes in the inner layer of the cell wall.

Prototheca wickerhamii--an alga infecting the hand

This report describes a hand infection caused by an alga. Prototheca wickerhamii. This rare organism presents most often as chronic dermatitis or bursitis of the upper extremity. Routine stains and cultures are easily confused with fungi. Only early, radical excision of the involved structures will effect a cure.

First case of human protothecosis in Canada: laboratory aspects

A case of bursitis due to Prototheca wickerhamii is briefly reported. In histological sections the organism stained well with fungal stains, grey with silver methanamine and red with periodic acid Schiff reagent. This unicellular achlorophyllous alga was studied on common laboratory media. The characterization of the Prototheca sp. depends largely on wet mount microscopic examination from broth or agar cultures which ensures the observation of endosporulation and a consistent absence of budding. Otherwise the growth rate and the pasty white colonies may lead to an erroneous identification, most likely as a Cryptococcus sp. P. wickerhamii lends itself very well to standard physiological tests used for the identification of yeasts. The strain was found insensitive to 5-fluorocytosine. The MIC of amphotericin B was 0.15 microgram/ml.

Experimental protothecosis in labortory animals

Attemps were made to produce protothecosis in laboratory animals by intratesticular, intraperitoneal, intravenous and subcutaneous inoculation of Prototheca zopfii, P. wickerhamii and P stagnorta. Only intratesticular injection successfully caused infection, and of the inoculated protothecae, only P. zopfii and P. wickerhamii were recovered in culture from testicular material.

Susceptibility of Prototheca species to antifungal agents

Twenty isolates of Prototheca filamenta, Prototheca moriformis, Prototheca stagnora, Prototheca wickerhamii, and Prototheca zopfii were tested for in vitro susceptibility to five commonly used antifungal agents: amphotericin B, 5-fluorocytosine, griseofulvin, miconazole, and nystatin. The results revealed resistance to griseofulvin of all the Prototheca isolates tested and an inhibitory effect on P. filamenta by high 5-fluorocytosine concentrations (minimal inhibitory concentration [MIC] = 12.5 to 100 mug/ml; minimal fungicidal or algacidal concentration [MFC/MAC] = 50 to 100 mug/ml). P. filamenta isolates were also susceptible to miconazole (MIC = 0.1 to 0.5 mug/ml, MFC/MAC = 0.5 to 1 mug/ml); isolates of the other Prototheca species varied in regard to miconazole activity from susceptible to resistant (MIC = 1 - >100 mug/ml, MFC/MAC = 5 - >100 mug/ml). The Prototheca isolates revealed an in vitro susceptibility to the polyene antifungal agents, amphotericin B, and nystatin (MIC = 0.09 to 3.12 mug/ml and 0.19 to 12.5 mug/ml, respectively; MFC/MAC = 0.19 to 25 mug/ml and 0.75 to 25 mug/ml, respectively).

The ultrastructure of Prototheca wickerhamii

Two clinical isolates from Prototheca wickerhamii were freeze-dried, fixed and studied by electron microscopy and were also examined growing in culture medium by phase contrast light microscopy. Resting spores placed on fresh medium developed cytoplasmic extensions which sequestrated before proliferation occurred. In the presence of adequate nutrients vegetative spores grew and subdivided to form up to 12 endospores within large sporangia which ruptured to release free spores every 5--6 hours. These proliferating or vegetative spores contained much more endoplasmic reticulum and mitochondria than the resting spores which contained more lipid, and often starch granules as well, but relatively few membranous organelles.

Wound infection by Prototheca wickerhamii, a saprophytic alga pathogenic for man

Biopsy of a wound infection of the palmar fascia in a young diabetic woman revealed characteristic periodic acid-Schiff-positive Prototheca species cells with a rosette configuration and internal septation. Prototheca wickerhamii was cultured repeatedly from the wound drainage and the biopsy tissue. Several diagnostic features distinguishing Prototheca species, saprophytic algae, from yeasts are: the formation of endospores by mitosis; greater variation in cell size (2 to 15 mum); the presence of cytoplasmic granules, particularly in old cultures; and the absence of budding forms and pseudomycelia. The organism was resistant to 5-fluorocytosine and the minimal inhibitory concentration of amphotericin B was 12.5 mug/ml. With the exception of the tetracycline group, all other 16 antibacterial agents tested appeared completely ineffective in vitro. A synergism between amphotericin B and tetracycline was clearly demonstrated by the use of the checkerboard method. Infection by Prototheca species may be more common than presently realized due to the common expedient of identifying yeast-like isolates as "yeast--not Candida albicans."

[Generalized protothecosis in a fruit bat (Pteropus lylei)]

Prototheca organisms, histologically resembling Prototheca wickerhamii, were found in a fruit bat as a cause of a massive granulomatous lymphadenitis and splenitis and a widespread granulomatous meningoencephalitis. Focal lesions were also present in the myocardium, in skeletal muscles, and in the kidneys.

Identification of the Prototheca species by immunofluorescence

Studies were carried out to develop fluorescent antibody reagents for the identification of the Prototheca species and for their differentiation from morphologically similar fungi of various genera in formalin-fixed tissues. Antisera against representative isolates of P. filamenta, P. moriformis, P. stagnora, P. wickerhamii, and P. zopfii were produced in rabbits. Antiglobulins, labeled with fluorescein-isothiocyanate that intensely stained most cells of the homologous species, were selected for use as potential diagnostic reagents. By adsorbing the conjugates with selected heterologous cross-staining protothecae, reagents that were both sensitive and specific were obtained. Evaluation of the adsorbed conjugates with sections of tissue infected with protothecae, sections of tissue infected with morphologically similar fungi, and cultures of protothecae showed that these reagents are useful for the rapid and reliable identification of the Prototheca species.

Ocular protothecosis in a dog

Prototheca organisms were observed in both eyes of a collie dog. The dog was blind, and the vitreal space of each eye was filled with gray-white material. Nongranulomatous endophthalmitis was seen in both eyes and in one eye posterior synechia and hemorrhage were observed. The retinas were totally detached by exudate. Various amounts of exudate consisting mostly of protothecal cells were present within and above the choroid. Also, exudate teeming with organisms was attached to the choroidal aspect of the detached retinas. In one eye infection extended into and about the optic nerve.

A case of protothecosis in a dog

Cells closely resembling those of a Prototheca sp. were found in lesions of the rectal wall, kidney, and myocardium of a 31/2-year-old springer spaniel dog which died after a short illness characterised by colitis, emesis, and polydypsia.

Protothecosis in a dog

This is the first report of a spontaneous case of protothecosis in the dog, an infection with organisms of the algal genus Prototheca. Clinically the animal had chronic bilateral iritis accompanied by glaucoma of one eye and hypotony of the other, chronic nephritis, arthritis, and bloody diarrhea. Lesions containing the algae occurred in myocardium, liver, kidneys, para-adrenal connective tissue, brain, and eyes.