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

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.

Genome Sequences of Two Strains of Prototheca wickerhamii Provide Insight Into the Protothecosis Evolution

The Prototheca alga is the only chlorophyte known to be involved in a series of clinically relevant opportunistic infections in humans and animals, namely, protothecosis. Most pathogenic cases in humans are caused by Prototheca wickerhamii. In order to investigate the evolution of Prototheca and the genetic basis for its pathogenicity, the genomes of two P. wickerhamii strains S1 and S931 were sequenced using Nanopore long-read and Illumina short-read technologies. The mitochondrial, plastid, and nuclear genomes were assembled and annotated including a transcriptomic data set. The assembled nuclear genome size was 17.57 Mb with 19 contigs and 17.45 Mb with 26 contigs for strains S1 and S931, respectively. The number of predicted protein-coding genes was approximately 5,700, and more than 96% of the genes could be annotated with a gene function. A total of 2,798 gene families were shared between the five currently available Prototheca genomes. According to the phylogenetic analysis, the genus of Prototheca was classified in the same clade with A. protothecoides and diverged from Chlorella ~500 million years ago (Mya). A total of 134 expanded genes were enriched in several pathways, mostly in metabolic pathways, followed by biosynthesis of secondary metabolites and RNA transport. Comparative analysis demonstrated more than 96% consistency between the two herein sequenced strains. At present, due to the lack of sufficient understanding of the Prototheca biology and pathogenicity, the diagnosis rate of protothecosis is much lower than the actual infection rate. This study provides an in-depth insight into the genome sequences of two strains of P. wickerhamii isolated from the clinic to contribute to the basic understanding of this alga and explore future prevention and treatment strategies.

Prototheca-ID: a web-based application for molecular identification of Prototheca species

The genus Prototheca houses unicellular, achlorophyllous, yeast-like algae, widely distributed in the environment. Protothecae are the only known plants that have repeatedly been reported to infect vertebrates, including humans. Although rare, protothecosis can be clinically demanding, with an unpredictable and treatment-resistant behavior. Accurate identification of Prototheca species relies upon DNA sequence-based typing of the mitochondrially encoded CYTB gene. However, no bioinformatic tool for the processing and analyzing of protothecal sequence data exists. Moreover, currently available sequence databases suffer from a limited number of records and lack of or flawed sequence annotations, making Prototheca identification challenging and often inconclusive. This report introduces the Prototheca-ID, a user-friendly, web-based application providing fast and reliable speciation of Prototheca isolates. In addition, the application offers the users the possibility of depositing their sequences and associated metadata in a fully open Prototheca-ID database, developed to enhance research integrity and quality in the field of Protothecae and protothecosis. Database URL: The Prototheca-ID application is available at https://prototheca-id.org.

Cutaneous Protothecosis with Meningitis Due to Prototheca wickerhamii in an Immunocompetent Teenager: Case Report and Literature Review

Human protothecosis is a rare infection caused by Prototheca spp., which are environmental achloric algae ubiquitously existing in nature. Members of the genus of Prototheca usually cause localized infection that affects the skin or wounds. Systemic infection is extremely rare and tends to occur in immunocompromised patients. Here, we report a case of cutaneous protothecosis and meningitis due to Prototheca wickerhamii in an immunocompetent teenager who obtained full-body tattoos at the time of infection. To the best of our knowledge, this is the first description of P. wickerhamii isolated from both skin tissue and cerebrospinal fluid. The data contained in this report will increase our understanding of this pathogen and elucidate the most optimal treatment.

Characterization of Prototheca CYP51/ERG11 as a possible target for therapeutic drugs

Prototheca spp. are achlorophyllous algae, ubiquitous in nature. An increasing number of human and animal cases of Prototheca infection (protothecosis) are reported, and antifungal azoles, which inhibit sterol 14α-demethylase (CYP51/ERG11) involved in ergosterol biosynthesis, have empirically been used for the treatment of protothecosis. Although Prototheca, like fungi, has ergosterol in the cell membrane, efficacy of the antifungal azoles in the treatment of protothecosis is controversial. For investigating the interaction of azole drugs with Prototheca CYP51/ERG11, the CYP51/ERG11 genomic genes of four strains of P. wickerhamii and one strain each of P. cutis and P. miyajii were isolated and characterized in this study. Compared with the CYP51/ERG11 gene of chlorophyllous Auxenochlorella Protothecoides, it is possible that ProtothecaCYP51/ERG11 gene, whose exon-intron structure appeared to be species-specific, lost introns associated with the loss of photosynthetic activity. Analysis of the deduced amino acid sequences revealed that Prototheca CYP51/ERG11 and fungal CYP51/ERG11 are phylogenetically distant from each other although their overall structures are similar. Our basic in silico studies predicted that antifungal azoles could bind to the catalytic pocket of Prototheca CYP51/ERG11. It was also suggested that amino acid residues away from the catalytic pocket might affect the drug susceptibility. The results of this study may provide useful insights into the phylogenetic taxonomy of Prototheca spp. in relationship to the CYP51/ERG11 structure and development of novel therapeutic drugs for the treatment of protothecosis.

LAY SUMMARY

Cases of infection by microalgae of Prototheca species are increasing. However, effective treatment has not been established yet. In this study, gene and structure of Prototheca's CYP51/ERG11, an enzyme which might serve as a target for therapeutic drugs, were characterized for the first time.

Protothecosis in Dogs and Cats-New Research Directions

Protothecosis refers to disease of humans and animals caused by infection with fungus-like, colourless microalgae of the genus Prototheca. Although protothecosis remains an uncommon infection, increasing numbers of human and animal cases are being diagnosed worldwide. This review summarises major new findings in basic science (sequencing analyses of sterol 14α-demethylase (CYP51/ERG11) genes and organelle genomes of Prototheca wickerhamii) to elucidate taxonomic features of this pathogen. Furthermore, this review updates and summarises the clinical features, diagnosis and treatment of protothecosis in dogs and cats. This content of this review is based on information presented at the medical phycology symposium held in the 20th Congress of the International Society for Human and Animal Mycology ( https://www.isham.org/ ).

Genome sequencing of Prototheca zopfii genotypes 1 and 2 provides evidence of a severe reduction in organellar genomes

Prototheca zopfii (P. zopfii, class Trebouxiophyceae, order Chlorellales, family Chlorellaceae), a non-photosynthetic predominantly free-living unicellular alga, is one of the few pathogens belonging to the plant kingdom. This alga can affect many vertebrate hosts, sustaining systemic infections and diseases such as mastitis in cows. The aim of our work was to sequence and assemble the P. zopfii genotype 1 and genotype 2 mitochondrial and plastid genomes. Remarkably, the P. zopfii mitochondrial (38 Kb) and plastid (28 Kb) genomes are models of compaction and the smallest known in the Trebouxiophyceae. As expected, the P. zopfii genotype 1 and 2 plastid genomes lack all the genes involved in photosynthesis, but, surprisingly, they also lack those coding for RNA polymerases. Our results showed that plastid genes are actively transcribed in P. zopfii, which suggests that the missing RNA polymerases are substituted by nuclear-encoded paralogs. The simplified architecture and highly-reduced gene complement of the P. zopfii mitochondrial and plastid genomes are closer to those of P. stagnora and the achlorophyllous obligate parasite Helicosporidium than to those of P. wickerhamii or P. cutis. This similarity is also supported by maximum likelihood phylogenetic analyses inferences. Overall, the P. zopfii sequences reported here, which include nuclear genome drafts for both genotypes, will help provide both a deeper understanding of the evolution of Prototheca spp. and insights into the corresponding host/pathogen interactions.

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.

3-Bromopyruvate as an Alternative Option for the Treatment of Protothecosis

Protothecosis is an unusual infection of both humans and animals caused by opportunistically pathogenic microalgae of the genus Prototheca. Until now, no standardized treatment protocols exist for the protothecal disease, boosted by a remarkable resistance of Prototheca spp. to a wide array of antimicrobial agents currently available in clinical use. Consequently, there is an urgent need for new effective drugs against Prototheca algae. In this study, the anti-Prototheca activity of 3-bromopyruvate (3BP), either alone or in combination with amphotericin B (AMB) was assessed in vitro, as well as the cytotoxicity of 3BP toward the bovine mammary epithelial cells and murine skin fibroblasts. The mean minimum inhibitory concentrations (MIC) and minimum algaecidal concentrations (MAC) were 0.85 ± 0.21 and 2.25 ± 0.54 mM for Prototheca wickerhamii, 1.25 ± 0.47 and 4.8 ± 1.03 mM for Prototheca blaschkeae, and 1.55 ± 0.69 and 5.6 ± 1.3 mM for Prototheca zopfii gen. 2, respectively. For all Prototheca strains tested, a synergistic interaction between 3BP and AMB was observed, resulting in about 4-fold reduction of their individual MICs, when used together. The elevated content of intracellular glutathione (GSH) was associated with a decreased susceptibility to 3BP. Both epithelial and fibroblast cells retained high viability upon treatment with 3BP at concentrations equivalent to the highest MIC recorded (3 mM) and 10-fold higher (30 mM), with the mean cell viability exceeding 80%, essentially the same as for the untreated cells. The results from these in vitro studies emphasize the high activity of 3BP against the Prototheca algae, its synergistic effect when used in combination with AMB, and the safety of the drug toward the tested mammalian cells. Along with the advantageous physico-chemical and pharmacokinetic properties, 3BP may be considered an effective and safe novel agent against the protothecal disease.

Clinicopathological features and course of cutaneous protothecosis

BACKGROUND

Protothecosis is an uncommon infection caused by the achlorophyllic algae found more commonly in tropical areas. Only a limited number of cases have been reported.

OBJECTIVE

We aimed to evaluate the clinicopathological features and treatment outcomes of cutaneous protothecosis.

METHODS

We retrospectively identified 20 pathology-confirmed cases of cutaneous protothecosis based on skin biopsies in two tertiary medical centres in Taiwan from 1997 to 2015.

RESULTS

The age of the patients at the time of diagnosis ranged from 48 to 85 years (mean age of 74 years). All lesions developed on the limbs. Twelve (60%) patients had adrenal insufficiency, but no patients had active malignancy at diagnosis. Interestingly, four (20%) patients had concurrent scabies infestation. Clinically, most lesions were erythematous plaques studded with punctate ulcers. Microscopically, the most common finding was granulomatous inflammation. Nineteen (95%) cases were successfully treated with itraconazole for 14-148 days with only one case of recurrence. Concomitant scabies should be suspected if pruritus is recalcitrant despite itraconazole treatment.

CONCLUSION

Despite its rarity, cutaneous protothecosis has become more significant due to an increased prevalence of immunocompromised individuals. Steroid overuse or iatrogenic adrenal insufficiency predisposes individuals to high-risk infections. Neglecting the disease leads to a chronic and incurable state. Protothecosis should be suspected in chronic eczematous and ulcerative plaques on the limbs refractory to conventional antibacterial and antiviral treatments, especially in patients with adrenal insufficiency. Clinical suspicion should be confirmed by skin biopsies, and confirmed cases can be successfully treated with itraconazole.

Case report of cutaneous protothecosis caused by Prototheca wickerhamii designated as genotype 2 and current status of human protothecosis in Japan

An 85-year-old Japanese woman presented with infiltrative erythema and ulceration on the extensor surface of her right forearm. Direct microscopic examination demonstrated spherical and morula-like sporangia, while histopathology revealed numerous microorganisms with a mulberry-like appearance in the dermis. Staining of the microorganisms also showed mulberry-like sporangia that resembled the spokes of a wheel. The isolated yeast-like microorganism had been identified as Prototheca wickerhamii genotype 2 in another independent study on the basis of its morphological, biochemical and genetic analysis. This case of protothecosis was recorded in Kyushu, Japan, and oral treatment with itraconazole 200 mg/day for 2 months was effective. Herein, we also summarize and analyze 39 cases of human protothecosis reported in Japan since the first record in 1983.

Isobaric tag for relative and absolute quantitation-based comparative proteomic analysis of human pathogenic Prototheca zopfii genotype 2 and environmental genotype 1 strains

BACKGROUND/PURPOSE

Prototheca species are ubiquitous achlorophyllic microalgae belonging to the family Chlorellaceae, which can cause a wide range of infections in humans and animals. Mainly in individuals with immunologic defects or trauma, Prototheca spp. can cause even lethal diseases. However, the exact pathogenic mechanism of Prototheca in causing disease remains largely unknown. To investigate the differences between pathogenic and nonpathogenic Prototheca spp. genotypes on proteome level, a nonpathogenic Prototheca zopfii genotype 1 strain, isolated from cow manure, and a human pathogenic P. zopfii genotype 2, isolated from human granulomatous lymphadenitis, were studied.

METHODS

Differentially expressed proteins between the two genotypes were quantified by isobaric tag for relative and absolute quantitation-based quantitative proteomics, using liquid chromatography-tandem mass spectrometry.

RESULTS

A total of 245 proteins were identified from the proteomic analysis after data filtering to eliminate low-scoring spectra. Among these, 35 proteins that displayed a significant (p<0.05) 1.5-fold change were considered as differentially expressed proteins.

CONCLUSION

The differentially expressed proteins were associated with suppressed energy production and conversion, carbohydrate transport and metabolism, and enhanced translation in the genotype 2 strain, and are thus potentially relevant in the pathogenic mechanism of P. zopfii genotype 2, but need further investigation.

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.

Internal transcribed spacer sequence-based rapid molecular identification of Prototheca zopfii and Prototheca blaschkeae directly from milk of infected cows

The increasing incidence of rare mastitis-causing pathogens has urged the implementation of fast and efficient diagnostic and control measures. Prototheca algae are known to be associated with diseases in humans and animals. In the latter, the most prevalent form of protothecosis is bovine mastitis with Prototheca zopfii and Prototheca blaschkeae representing the most common pathogenic species. These nonphotosynthetic and colorless green algae are ubiquitous in different environments and are widely resistant against harmful conditions and antimicrobials. Hence, the association of Prototheca with bovine mastitis represents a herd problem, requiring fast and easy identification of the infectious agent. The purpose of this study was to develop a reliable and rapid method, based on the internal transcribed spacer (ITS) sequences of ribosomal DNA, for molecular identification and discrimination between P. zopfii and P. blaschkeae in bovine mastitic milk. The complete ITS sequences of 32 Prototheca isolates showed substantial interspecies but moderate intraspecies variability facilitating the design of species-specific PCR amplification primers. The species-specific PCR was successfully applied to the identification of P. zopfii and P. blaschkeae directly from milk samples. The intraspecific ITS phylogeny was compared for each species with the geographical distribution of the respective Prototheca isolates, but no significant correlation was found.

Simultaneous identification by multiplex PCR of major Prototheca spp. isolated from bovine and buffalo intramammary infection and bulk tank

Bovine mastitis caused by Prototheca spp. infection is increasing worldwide, therefore becoming more relevant to the dairy industry. Almost all Prototheca isolates from bovine mammary protothecosis came from P. zopfii genotype 2, with a lower prevalence of infection due to P. blaschkeae and rarely to P. wickerhamii. In this study, we report the development of two multiplex PCR assays able to discriminate among the three species responsible for bovine intramammary infection (IMI). Our assay is based on the specific amplification of new DNA target from mitochondria and chloroplasts partial sequences, of different Prototheca isolates. Both methods were set up using reference strains belonging to all Prototheca species and validated by the analysis of 93 isolates from bovine and buffalo IMI and bulk tank milk samples. The investigation involves 70 isolates from North, 13 from Central and 10 from South Italian regions. Isolates from bovine were most commonly identified as P. zopfii genotype 2, and only in one case as P. blaschkeae, whereas isolates from buffaloes belonged both to P. zopfii genotype 2 and P. wickerhamii. These findings proved the suitability of our multiplex PCRs as a rapid test to discriminate among pathogenic Prototheca strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work reports PCR assays based on novel Prototheca spp. mitochondrial and chloroplastic target sequences. The multiplex PCR protocol described in this study is useful for rapid simultaneous detection of P. zopfii, P. wickerhamii and P. blaschkeae.