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

Outbreak of Prototheca wickerhamii algaemia and sepsis in a tertiary care chemotherapy oncology unit

BACKGROUND

Prototheca is an emerging, opportunistic, pathogenic, zoonotic achlorophyllous green alga, expanding in pathogenicity and host range, causing localized and disseminated infections. This outbreak of Prototheca wickerhamii algaemia and sepsis in a tertiary care 30-bedded chemotherapy oncology unit is the first human outbreak to the best of our knowledge.

METHODS

P. wickerhamii algaemia was confirmed on consecutive isolation. Person to person transmission was hypothesized considering all patients in the unit at risk. Clinico-demographic, diagnostic and treatment profile were correlated. Both manual and automated systems were used for blood culture, isolation, identification and susceptibility of Prototheca. Liposomal amphotericin B was given. Outbreak surveillance of faeces, fingertips and environmental reservoirs, retrospective surveillance during past 15 years and prospective surveillance was continued for two years.

RESULTS

The outbreak affected 12 neutropenic patients over 50 days. No specific clinical features were noted. The hypothesis could not be substantiated. P. wickerhamii was isolated as yeast-like colonies revealing Gram positive yeast-like cells without budding and pseudohyphae which were confirmed by automated system. Post amphotericin B blood cultures were negative for Prototheca. Surveillance studies were not contributory.

CONCLUSION

P. wickerhamii has no documented reservoirs or transmission. Endogenous colonization in the gut followed by translocation during chemotherapy induced immunosuppression is likely to cause algaemia and sepsis. Outbreaks are difficult to detect and control as incubation period is variable and clinical presentation is muted, emphasizing the need to strengthen hospital and laboratory based surveillance systems to ensure adequate preparedness, rapid detection and response to outbreaks.

Disseminated protothecosis in a Mexican child

Protothecosis is a rare human infection. There are 3 clinical forms: cutaneous, olecranon bursitis and systemic. Here we present the first case of disseminated protothecosis in Mexico in an immunocompetent girl whose lesions were mostly dermatologic. The patient was successfully treated with amphotericin B colloidal dispersion and gentamicin, followed by itraconazole.

Prototheca wickerhamii algaemia presenting as cholestatic hepatitis in a patient with systemic lupus erythematosus: A case report and literature review

Human protothecal infection is uncommon and could be localized or systemic disease. Disseminated Prototheca algaemia tends to occur in immunocompromised patients (solid organ transplants, hematological malignancies) with high mortality. Diagnosis could be missed or delayed due to unusual clinical presentation and/or under-recognition of characteristic microscopic features of Prototheca species. Combined approach that includes removal of source of infection and intravenous amphotericin B provides the best chance of cure.

Prototecose: uma doença emergente

Prototecose, causada por Prototheca zopfii ou P. wickerhamii, é uma doença emergente em animais e humanos. Em bovinos, P. zopfii é uma importante causa de mastite ambiental. Em cães e gatos, a prototecose é causada principalmente por P. zopfii. Em cães, causa infecção cutânea ou uma forma sistêmica envolvendo diversos órgãos. Em gatos, predominam as lesões tegumentares na região da face e plano nasal. No homem, a prototecose, causada principalmente por P. wickerhamii, manifesta-se sob três formas: cutânea, articular com bursite do olécrano e sistêmica. Pode ocorrer em indivíduos imunocompetentes, os quais podem apresentar bursite e/ou infecções cutâneas localizadas, ou em indivíduos imunossuprimidos, nos quais a enfermidade pode ser disseminada e/ou com envolvimento visceral. A prototecose causada por P. wickerhamii foi descrita recentemente em caprinos como causa de rinite afetando o vestíbulo nasal, união mucocutânea, pele da face e orelha. Nesta revisão são abordadas as características microbiologias e susceptibilidade a antimicrobianos do agente, e a epidemiologia, sinais clínicos, patologia, diagnóstico, tratamento e controle da prototecose em animais domésticos e no homem.

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.

Multiple metabolic roles for the nonphotosynthetic plastid of the green alga Prototheca wickerhamii

The presence of plastids in diverse eukaryotic lineages that have lost the capacity for photosynthesis is well documented. The metabolic functions of such organelles, however, are poorly understood except in the case of the apicoplast in the Apicomplexa, a group of intracellular parasites including Plasmodium falciparum, and the plastid of the green alga Helicosporidium sp., a parasite for which the only host-free stage identified in nature so far is represented by cysts. As a first step in the reconstruction of plastid functions in a nonphotosynthetic, predominantly free-living organism, we searched for expressed sequence tags (ESTs) that correspond to nucleus-encoded plastid-targeted polypeptides in the green alga Prototheca wickerhamii. From 3,856 ESTs, we found that 71 unique sequences (235 ESTs) correspond to different nucleus-encoded putatively plastid-targeted polypeptides. The identified proteins predict that carbohydrate, amino acid, lipid, tetrapyrrole, and isoprenoid metabolism as well as de novo purine biosynthesis and oxidoreductive processes take place in the plastid of P. wickerhamii. Mg-protoporphyrin accumulation and, therefore, plastid-to-nucleus signaling might also occur in this nonphotosynthetic organism, as we identified a transcript which encodes subunit I of Mg-chelatase, the enzyme which catalyzes the first committed step in chlorophyll synthesis. Our data indicate a far more complex metabolism in P. wickerhamii's plastid compared with the metabolic pathways predicted to be located in the apicoplast of P. falciparum and the plastid of Helicosporidium sp.

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.

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.

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.

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.

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.

[Preliminary investigation of the in vitro inhibitory effect of antibiotics on algae of the genus Prototheca]

We investigated the possible inhibitory action 'in vitro' by antibiotic containing discs against microscopic alga that are potential human pathogens of the genus Prototheca especially P. wickerhamii. The results indicated that inhibitors in vitro included amikacin, colistin, dibecacin, framicetin, gentamycin, kanamycin, lividomycin, neomycin, polymyxin, paromomycin, ribostamycin, sisomycin and tobramycin. We emphasize the interest in the effectiveness at these drugs in a case of human protothecosis.

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.

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).