Prototheca wickerhamii mimicking yeast: a cautionary tale

Successful treatment of cutaneous protothecosis with fluconazole: A case report and epidemiology study of Prototheca infection in China

BACKGROUND

Protothecosis is an infection of humans and animals caused by a rare conditionally pathogenic fungus (prototheca). It can occur in immunocompromised or normal patients.

AIMS

To describe the epidemiology of prototheca infection in China.

METHODS

We report a case of successful treatment of cutaneous protothecosis with fluconazole and analyzed the epidemiological characteristics, risk factors, clinical manifestations, diagnosis, treatment and prognosis of prototheca infections in China.

RESULTS

We describe this case and 29 cases of prototheca infections in China. At present, Prototheca wickerhamii (Pw) infection is the most common infection in China, and single or combined itraconazole is the preferred treatment.

CONCLUSIONS

These results provide detailed information and relevant clinical treatment strategies for the diagnosis and treatment of protothecosis in China.

Human Disseminated Protothecosis: The Skin is the "Window"?

Human disseminated protothecosis is a rare infection caused by members of the genus Prototheca, an achlorophyllic algae always associated with debilitated hosts. The presence of non-budding cells and large, spherical cells (sporangia) with endosporulation (morula) in histology is proof of Prototheca infection. Regrettably, due to the lack of specificity of clinical features and low awareness among clinicians, protothecosis is always underestimated and misdiagnosed. The available data on a species-specific analysis of this infection are limited. In this review, we summarize the etiological, epidemiological, and clinical aspects of disseminated protothecosis. The potential pathogenicity and clinical differences between P. zopfii and P. wickerhamii were observed. Additionally, the skin not only became the main invasion site but also the most involved organ by the pathogen. With the increasing numbers of immunocompromised individuals throughout the world, the incidence of disseminated infection caused by Prototheca is bound to increase, and disseminated protothecosis that accompanies skin symptoms should be taken into account by clinicians.

Protothecosis in the mucosa of the pharynx mimicking pharyngeal cancer in an immunocompetent individual: a case report

Background

Protothecosis is a rare infection in humans and animals caused by the achlorophyllic algae Prototheca species. More than half of the protothecosis cases are cutaneous infections, and most cases are observed in immunocompromised individuals.

Case presentation

We report a case of Prototheca wickerhamii infection in the mucosa of the pharynx in a 53-year-old immunocompetent woman with an incidentally found mass lesion at the left tongue base. Histopathological findings of the mass lesion suggested cryptococcosis, but P. wickerhamii was identified from the oropharynx scrape culture based on DNA sequencing. After surgical resection, fosfluconazole treatment was initiated, and subsequently, treatment was switched to topical amphotericin B. The residual mass lesion did not deteriorate during the 4-month antifungal treatment and 1-year observational period.

Conclusions

Prototheca species can be easily misdiagnosed as yeasts because of their morphological and pathological similarities. Prototheca, in addition to Cryptococcus should be considered if slow-growing, large Gram-positive organisms are encountered. Lactophenol cotton blue staining of the colony helps distinguish these organisms. Further study is needed to determine the appropriate treatment according to the infection focus.

Molecular characterization of Prototheca in 11 symptomatic dogs

Protothecosis is an uncommon disease caused by algae of the genus Prototheca. In dogs, the infection is usually first localized to the colon but has the propensity to later disseminate hematogenously to many other organs, with marked tropism for the eyes and central nervous system. Diagnosis is established by culture and/or evidence of Prototheca organisms in cytologic or histologic preparations. Species characterization, however, requires molecular investigations. Our laboratory set up a real-time PCR targeting portion D1/D2 of the 28S rRNA for identification of Prototheca species from both positive cultures (of rectal swabs and urine) and formalin-fixed, paraffin-embedded tissue. Prototheca bovis, P. ciferrii, and P. wickerhamii were characterized in 11 dogs with systemic or cutaneous protothecosis. Prototheca identifications were phylogenetically consistent with the new taxonomy proposed for this genus based on the mitochondrial cytochrome b gene. As a pilot study, we screened feces and rectal scrapes from 200 asymptomatic dogs, using 2 cohorts of stray and owned animals, to determine the prevalence of intestinal carriage of Prototheca spp. The Prototheca-negative results from both cohorts of healthy dogs suggest that predisposing factors related to the host probably contribute more to the acquisition of clinical disease than exposure to contaminated environments.

cytb as a New Genetic Marker for Differentiation of Prototheca Species

Achlorophyllous unicellular microalgae of the genus Prototheca (Trebouxiophyceae, Chlorophyta) are the only known plants that cause infections in both humans and animals, collectively referred to as protothecosis. Human protothecosis, most commonly manifested as cutaneous, articular, and disseminated disease, is primarily caused by Protothecawickerhamii, followed by Protothecazopfii and, sporadically, by Protothecacutis and Protothecamiyajii In veterinary medicine, however, P. zopfii is a major pathogen responsible for bovine mastitis, which is a predominant form of protothecal disease in animals. Historically, identification of Prototheca spp. has relied upon phenotypic criteria; these were later replaced by molecular typing schemes, including DNA sequencing. However, the molecular markers interrogated so far, mostly located in the ribosomal DNA (rDNA) cluster, do not provide sufficient discriminatory power to distinguish among all Prototheca spp. currently recognized. Our study is the first attempt to develop a fast, reliable, and specific molecular method allowing identification of all Prototheca spp. We propose the mitochondrial cytb gene as a new and robust marker for diagnostics and phylogenetic studies of the Prototheca algae. The cytb gene displayed important advantages over the rDNA markers. Not only did the cytb gene have the highest discriminatory capacity for resolving all Prototheca species, but it also performed best in terms of technical feasibility, understood as ease of amplification, sequencing, and multiple alignment analysis. Based on the species-specific polymorphisms in the partial cytb gene, we developed a fast and straightforward PCR-restriction fragment length polymorphism (RFLP) assay for identification and differentiation of all Prototheca species described so far. The newly proposed method is advocated to be a new gold standard in diagnostics of protothecal infections in human and animal populations.

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.

Successful treatment of cutaneous protothecosis with liposomal amphotericin and oral itraconazole

Protothecosis is a rare algal infection, affecting primarily immunocompromised hosts. Optimal management is unclear: in-vitro antimicrobial breakpoints are not established and therapeutic decisions are primarily based on case reports. We present a case of cutaneous Prototheca wickerhamii infection in an immunosuppressed 63 year old male, successfully treated with liposomal amphotericin and prolonged itraconazole. Inoculation may have been through frequent hot-tub use, highlighting hot-tub exposure as an infection risk for the immunocompromised host.

Protothecal bursitis after simultaneous kidney/liver transplantation: a case report and review

Solid organ transplantation is an accepted therapy for end-stage diseases of the kidneys, liver, heart, and lungs. Unfortunately, transplantation is associated with infectious complications. Here, we present a case report of Prototheca wickerhamii olecranon bursitis and review all of the cases in solid organ transplant (SOT) recipients published in the literature to date. In our patient, the infection resolved with surgical therapy and limited antifungal therapy, and no symptoms have recurred over 24 months of follow-up. A review of the literature suggests that 50% of SOT recipients with Prototheca infection present with disseminated infection, and the overall mortality is 75%. More studies are required to determine the optimal management of protothecosis in this population.

Prototheca wickerhamii algaemia: an emerging infection in solid organ transplant recipients

Prototheca wickerhamii is an alga that rarely causes human disease but has been reported increasingly among immunocompromised individuals. We report a fatal case of P. wickerhamii in a renal transplant recipient who presented with a cutaneous lesion that led to disseminated disease despite treatment with voriconazole. We reviewed previous cases of protothecosis involving solid organ transplant recipients in the literature and discussed the value of newer microbiology platforms, i.e., matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF), to achieve early diagnosis and impact outcomes.

Fungus or parasite or both: a diagnostic challenge

Protothecosis is a rare opportunistic infection caused by achlorophilic algae Prototheca wickerhamii, mainly in immunocompromised hosts. Due to their morphologic appearance in routine culture media, they can often mimic yeast-like opportunistic pathogens such as Pneumocystis jirovecii. This can delay the identification of other culprit organisms. We present a fatal case of protothecosis in a 74-year-old immunosuppressed male with concomitant Pneumocystis jirovecii pneumonia (PJP). The presence of a coinfection along with resemblance in routine culture media and microbiological and histopathological staining can prove to be a diagnostic challenge and delay appropriate care of an immunosuppressed patient.

Ribosomal internal transcribed spacer of Prototheca wickerhamii has characteristic structure useful for identification and genotyping

Prototheca species are achlorophyllous algae ubiquitous in nature and known to cause localized and systemic infection both in humans and animals. Although identification of the Prototheca species in clinical specimens is a challenge, there are an increasing number of cases in which molecular techniques have successfully been used for diagnosis of protothecosis. In this study, we characterized nuclear ribosomal DNA (rDNA) of a strain of Prototheca (FL11-0001) isolated from a dermatitis patient in Japan for its species identification. When nuclear rDNA of FL11-0001 and that of various other Prototheca strains were compared by polymerase chain reaction (PCR), the results indicated that the sizes of ribosomal internal transcribed spacer (ITS) were different in a species-dependent manner, suggesting that the variation might be useful for differentiation of Prototheca spp. Especially, ITS of P. wickerhamii, the most common cause of human protothecosis, was distinctively larger than that of other Prototheca spp. FL11-0001, whose ITS was comparably large, could easily be identified as P. wickerhamii. The usefulness of the PCR analysis of ITS was also demonstrated by the discovery that one of the clinical isolates that had previously been designated as P. wickerhamii was likely a novel species. Furthermore, our data demonstrated that nucleotide sequences of P. wickerhamii ITS are heterogenous between different rDNA copies in each strain and also polymorphic between strains. Phylogenetic analysis suggested that the ITS sequences could be classified to four clades, based on which P. wickerhamii strains might be grouped into at least two genotypes. Comprehensive characterization of Prototheca rDNA may provide valuable insights into diagnosis and epidemiology of protothecosis, as well as evolution and taxonomy of Prototheca and related organisms.

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.

A rare case of prototheca algaemia in a patient with systemic lupus erythematosus and recent belimumab infusion

Novel agents for the treatment of immune-mediated diseases such as systemic lupus erythematosus (SLE) have been increasingly used as an alternative to or in combination with conventional therapies. Belimumab, a human monoclonal antibody that inhibits B-cell activating factor (BAFF), has demonstrated efficacy in moderate-to-severe SLE with similar adverse effects when compared to other biologic agents and conventional SLE therapies. Here, we describe a woman with SLE and diabetes mellitus (DM) on immunosuppressive therapy for five years who was admitted to the hospital for pneumonia but had a complicated hospital course with multiple infections and, most notably, a nosocomial algaemia due to Prototheca wickerhamii, which was treated successfully with amphotericin B. She had recently received three belimumab infusions as an outpatient prior to admission to the hospital. To the best of our knowledge no cases of human protothecosis in patients receiving belimumab have been described in the English literature; however, unusual infections have to be considered in all patients undergoing immunosuppressive therapies who persist with fever despite conventional antimicrobials.

Galactomannan enzymatic immunoassay cross-reactivity caused by Prototheca species

We report a reactive Aspergillus galactomannan enzymatic immunoassay against the serum of a patient with invasive Prototheca zopfii infection. Analysis of the supernatants of suspensions of P. zopfii and other Prototheca isolates revealed positive results as well. These data suggest cross-reactivity with the serum Aspergillus galactomannan assay in invasive protothecosis.

Case report: Infrapatellar bursitis caused by Prototheca wickerhamii

A 54-year-old immunocompetent man presented with an infrapatellar bursitis caused by Prototheca wickerhamii. Because of clinical and microbiological relapse two weeks after bursectomy, six weekly injections of 5 mg of conventional amphotericin B were chosen for intrabursal treatment. Four months after completion of the treatment, the patient remains cured.