Pythium insidiosum: an overview

Development of an Anti-Elicitin Antibody-Based Immunohistochemical Assay for Diagnosis of Pythiosis

Pythiosis is an emerging and life-threatening infectious disease of humans and animals living in tropical and subtropical countries and is caused by the fungus-like organism Pythium insidiosum. Antifungals are ineffective against this pathogen. Most patients undergo surgical removal of the infected organ, and many die from advanced infections. Early and accurate diagnosis leads to prompt management and promotes better prognosis for affected patients. Immunohistochemical assays (IHCs) have been developed using rabbit antibodies raised against P. insidiosum crude extract, i.e., culture filtrate antigen (CFA), for the histodiagnosis of pythiosis, but cross-reactivity with pathogenic fungi compromises the diagnostic performance of the IHC. Therefore, there is a need to improve detection specificity. Recently, the elicitin protein, ELI025, was identified in P. insidiosum, but it was not identified in other human pathogens, including true fungi. The ELI025-encoding gene was successfully cloned and expressed as a recombinant protein in Escherichia coli. This study aims to develop a new IHC using the rabbit anti-ELI025 antibody (anti-ELI) and to compare its performance with the previously reported anti-CFA-based IHC. Thirty-eight P. insidiosum histological sections stained positive by anti-ELI-based and anti-CFA-based IHCs indicating 100% detection sensitivity for the two assays. The anti-ELI antibody stained negative for all 49 negative-control sections indicating 100% detection specificity. In contrast, the anti-CFA antibody stained positive for one of the 49 negative controls (a slide prepared from Fusarium-infected tissue) indicating 98% detection specificity. In conclusion, the anti-ELI based IHC is sensitive and specific for the histodiagnosis of pythiosis and is an improvement over the anti-CFA-based assay.

Surgical and Medical Treatment of Pyloric and Duodenal Pythiosis in a Dog

A 5 yr old, male, neutered mixed-breed dog was referred for persistent vomiting 2 wk following a pyloric biopsy for a pyloric outflow obstruction. Histopathology at the time of initial surgery was suggestive of pythiosis. Following referral, the dog underwent radical surgical treatment with a Billroth II procedure, partial pancreatectomy, and cholecystoduodenostomy. Histopathology and serology confirmed the diagnosis of pythiosis and medical treatment consisting of itraconazole and terbinafine was started postoperatively. Serology titers were checked again at 8, 12, and 24 wk postoperatively revealing a positive response to treatment and no reoccurrence of pythiosis. Since surgery, the patient experienced waxing and waning elevations of liver values and laparoscopic liver biopsies 10 mo postoperatively revealed hepatic cirrhosis with fibrosis, bile duct hyperplasia, and chronic inflammation. This report documents successful treatment of pyloric/duodenal pythiosis and the long-term (17 mo) consequences associated with the Billroth II, partial pancreatectomy, and biliary rerouting in the dog.

In Vitro Synergism between Azithromycin or Terbinafine and Topical Antimicrobial Agents against Pythium insidiosum

We describe here in vitro activity for the combination of azithromycin or terbinafine and benzalkonium, cetrimide, cetylpyridinium, mupirocin, triclosan, or potassium permanganate. With the exception of potassium permanganate, the remaining antimicrobial drugs were active and had an MIC90 between 2 and 32 μg∕ml. The greatest synergism was observed for the combination of terbinafine and cetrimide (71.4%). In vivo experimental evaluations will clarify the potential of these drugs for the topical treatment of lesions caused by Pythium insidiosum.

Pythiosis in the Nasal Cavity of Horses

Two cases of nasal pythiosis are reported in horses from the semi-arid region of northeastern Brazil. From January 1986 to December 2015, the Laboratory of Animal Pathology, Federal University of Campina Grande received 830 equine samples, 156 (18.79%) of which were diagnosed with pythiosis. Of these, two horses (1.28%), a male and a female adult cross-breed, had lesions in the nasal cavity. Both horses had access to water reservoirs. Clinically, they had swelling in the rhinofacial region and a serosanguineous nasal discharge. Macroscopically, in case 1, the lesion affected the nasal vestibule, extending to the alar cartilage and nasal septum. In case 2, the lesion extended through the turbinates and the meatuses of the nasal cavity, as well as the ethmoid region. In both cases, the lesions were characterized by having a yellow-grey granular surface with cavitations of different sizes containing coral-like masses of necrotic tissue (kunkers). Histologically, multifocal necrotizing eosinophilic rhinitis associated with hyphae (2-8 μm) similar to Pythium insidiosum were observed. In case 2, the lesions extended to the muscle, cartilage and bone adjacent to the nasal cavity and lungs. The diagnosis was confirmed by immunohistochemistry. It is concluded that nasal pythiosis occurs sporadically in horses in the semi-arid region of northeastern Brazil where cutaneous pythiosis is prevalent.

Pythium insidiosum: inhibitory effects of propolis and geopropolis on hyphal growth

Propolis and geopropolis are resinous products of bees showing antimicrobial effects. There is no data concerning their action against Pythium insidiosum - the causative agent of pythiosis, a pyogranulomatous disease of the subcutaneous tissue that affects mostly horses, dogs and humans. Fragments of 15 isolates of P. insidiodum were incubated with propolis and geopropolis extracts and evaluated for up to seven days to detect the minimal fungicidal concentration (MFC). Propolis inhibited three isolates at 1.0mgmL^-1 after 24h and all other isolates at 3.4mgmL^-1. Geopropolis led to more variable results, exerting predominantly a fungistatic action than a fungicidal one. Propolis was more efficient than geopropolis in inhibiting P. insidiosum since lower concentrations led to no growth after 24h. This effect may be due to propolis chemical composition, which has more active compounds than geopropolis. Propolis seemed to be a good candidate for in vivo studies, since treatment with conventional antifungal compounds is difficult in most of the cases, requiring extensive surgical debridement.

Cutaneous pythiosis in a donkey (Equus asinus) in Brazil

Our study describes the clinical, epidemiologic, pathologic, immunohistochemical, and molecular aspects PCR of a case of cutaneous pythiosis in a donkey (Equus asinus) from Brazil. During a dry period, the animal grazed for 4 months around a pond where the vegetation remained green. Skin lesions were nodular, multifocal, and disseminated, mainly involving the legs, ventral chest, and mammary gland. On cut surface, there were multifocal to coalescent discrete yellow foci, and occasional small cavitations with a few kunkers. Ulcerative nodular pyogranulomatous and eosinophilic dermatitis with folliculitis and furunculosis were observed histologically. Hyphae were observed in sections stained with Gomori methenamine silver. Immunohistochemistry with Pythium insidiosum antibodies yielded strong immunostaining of hyphae. P. insidiosum DNA was extracted from tissues in paraffin blocks by amplification of a fragment of 105 bp, which targets the 5.8S ribosomal gene. After the diagnosis of pythiosis, the larger skin lesions were excised and treated as second intention healing wounds, which were completely healed 30 days after resection. Small skin lesions regressed spontaneously in ~60 days. The granulomatous inflammation and outcome of the disease in this donkey were similar to cases of pythiosis in cattle.

Protein A/G-based immunochromatographic test for serodiagnosis of pythiosis in human and animal subjects from Asia and Americas

Pythiosis is a life-threatening infectious disease of both humans and animals living in Asia, Americas, Africa, and parts of Australia and New Zealand. The etiologic pathogen is the fungus-like organism Pythium insidiosum The disease has high mortality and morbidity rates. Use of antifungal drugs are ineffective against P. insidiosum, leaving radical surgery the main treatment option. Prompt treatment leads to better prognosis of affected individuals, and could be achieved by early and accurate diagnosis. Since pythiosis has been increasingly reported worldwide, there is a need for a rapid, user-friendly, and efficient test that facilitates the diagnosis of the disease. This study aims to develop an immunochromatographic test (ICT), using the bacterial protein A/G, to detect anti-P. insidiosum IgGs in humans and animals, and compare its diagnostic performance with the established ELISA. Eighty-five serum samples from 28 patients, 24 dogs, 12 horses, 12 rabbits, and 9 cattle with pythiosis, and 143 serum samples from 80 human and 63 animal subjects in a healthy condition, with thalassemia, or with other fungal infections, were recruited for assay evaluation. Detection specificities of ELISA and ICT were 100.0%. While the detection sensitivity of ELISA was 98.8%, that of ICT was 90.6%. Most pythiosis sera, that were falsely read negative by ICT, were weakly positive by ELISA. In conclusion, a protein A/G-based ICT is a rapid, user-friendly, and efficient assay for serodiagnosis of pythiosis in humans and animals. Compared to ELISA, ICT has an equivalent detection specificity and a slightly lower detection sensitivity.

Outcomes and factors influencing prognosis in patients with vascular pythiosis

OBJECTIVE

Vascular pythiosis, caused by Pythium insidiosum, is associated with a high mortality rate. We reviewed the outcomes and established the factors predicting prognosis of patients treated in our institution with surgery, antifungal therapy, or immunotherapy.

METHODS

We undertook a retrospective record review of patients with vascular pythiosis treated in Siriraj Hospital, Bangkok, Thailand, between January 2005 and January 2015. Patient characteristics, type of surgery, adjunctive antifungal treatment, adjunctive immunotherapy, and disease status of surgical arterial and surrounding soft tissue margins were recorded. We calculated the mortality rate and established factors predicting prognosis.

RESULTS

The records of 11 patients were reviewed. All patients had thalassemia. Nine patients (81.8%) had a history of contact with contaminated water. The clinical presentations were chronic ulcers (45.5%), toe gangrene (27.3%), pulsatile mass (27.3%), and acute limb ischemia (27.3%). Above-knee amputation was required in 10 patients (90.9%). The mortality rate was 36.4%. Independent variables between survivors and nonsurvivors were lack of an arterial disease-free surgical margin (P = .003), lack of a surrounding soft tissue disease-free surgical margin (P < .05), a suprainguinal lesion (P < .05) and duration of symptoms (P < .05). Adjuvant itraconazole, terbinafine, and Pythium vaccine have a role to play in patients with a disease-free arterial surgical margin but in whom infected surrounding soft tissue could not be completely excised.

CONCLUSIONS

Achieving adequate disease-free surgical margins-especially the arterial margin-at amputation or débridement is the most important prognostic factor in patients with vascular pythiosis. Early detection combined with a multidisciplinary approach to treatment, including surgery, antifungal agents, and immunotherapy, allows the best possible outcome to be obtained.

Description of three novel Lagenidium (Oomycota) species causing infection in mammals

BACKGROUND

Recent molecular phylogenetic analysis of Lagenidium strains recovered from subcutaneous lesions in cats, dogs, and a human with lagenidiosis resolved into four clades; one of them was Lagenidium giganteum, but three others were novel.

AIMS

Due to the recent increase in L. giganteum infections from mammals, we studied 21 Lagenidium strains isolated from dogs and a human available in our collection.

METHODS

Molecular phylogenetic studies and phenotypic characteristics were used to characterize the strains.

RESULTS

We report the finding of three novel species, herein designated as Lagenidium ajelloi, sp. nov., Lagenidium albertoi sp. nov, and Lagenidium vilelae sp. nov. Their morphological and growth features are also presented.

CONCLUSIONS

Our study revealed the presence of three novel Lagenidium species infecting mammals.

Occurrence and distribution of Malassezia species on skin and external ear canal of horses

The aim of this study was to investigate the prevalence of Malassezia species from the body skin and external ear canal of healthy horses. The samples were obtained by scraping the skin surface from the nose, groin and dorsum and swabbing from the external ear canal of 163 animals, and then incubated on sabouraud dextrose agar and modified Dixon agar. Malassezia species were isolated from 34.9% of horses. The percentages of Malassezia species were 64.3% for Arab, 35.7% for Persian, 35.4% for Thoroughbred and 27.1% for Turkmen breeds. The greatest abundance of Malassezia species was found in the external ear canal (47.7%, representing significant difference with other sites), followed by nose (26.3%), groin (15.8%) and dorsum (10.5%) (P < 0.05). A total of 57 strains from six Malassezia species were detected with a frequency rate as follows: M. pachydermatis (33.3%), M. globosa (26.3%), M. sympodialis (14.1%), M. restricta (10.5%), M. obtusa (8.8%) and M. furfur (7%). The most common age-group affected was 1-3 years (59.4%). This study confirmed that cutaneous Malassezia microbiota in healthy horses varies by body site and age but not by breed and gender, representing M. pachydermatis as the most prevalent species on horse skin.

In Vitro and In Vivo Antimicrobial Activities of Minocycline in Combination with Azithromycin, Clarithromycin, or Tigecycline against Pythium insidiosum

The present study investigated the in vitro and the in vivo interactions among azithromycin, clarithromycin, minocycline, and tigecycline against Pythium insidiosum. In vitro antimicrobial activities were determined by the broth microdilution method in accordance with CLSI document M38-A2, and the antibiotic interactions were assayed using the checkerboard MIC format. In vivo efficacy was determined using a rabbit infection model. The geometric mean MICs of azithromycin, clarithromycin, minocycline, and tigecycline against P. insidiosum were, respectively, 1.91, 1.38, 0.91, and 0.79 μg/ml. By checkerboard testing, all combinations resulted in in vitro synergistic interactions (>60%). Antagonism was not observed. The in vivo studies showed that azithromycin (20 mg/kg/day twice daily) alone or in combination with minocycline (10 mg/kg/day twice daily) significantly decreased the fungal burden. This study demonstrates that azithromycin possesses potent curative efficacy against subcutaneous pythiosis in the rabbit model.

Lagenidium giganteum pathogenicity in mammals

Strains pathogenic to mammals share phylogenetic and phenotypic features with strains approved for mosquito control.

Infections of mammals by species in the phylum Oomycota taxonomically and molecularly similar to known Lagenidium giganteum strains have increased. During 2013–2014, we conducted a phylogenetic study of 21 mammalian Lagenidium isolates; we found that 11 cannot be differentiated from L. giganteum strains that the US Environmental Protection Agency approved for biological control of mosquitoes; these strains were later unregistered and are no longer available. L. giganteum strains pathogenic to mammals formed a strongly supported clade with the biological control isolates, and both types experimentally infected mosquito larvae. However, the strains from mammals grew well at 25°C and 37°C, whereas the biological control strains developed normally at 25°C but poorly at higher temperatures. The emergence of heat-tolerant strains of L. giganteum pathogenic to lower animals and humans is of environmental and public health concern.

A biochemical screening approach to putatively differentiate mammalian pathogenic Oomycota species in the clinical laboratory

The report of four novel mammalian pathogenic species of the genus Lagenidium prompted us to study the use of biochemical assays to differentiate the Oomycota mammalian pathogens Pythium insidiosum and Lagenidium spp. We investigated the reaction of 23 Lagenidium and eight Pythium species in various biochemical assays. Because the morphological features of the Oomycota species are similar to those of species in the Entomophthoramycota and Mucormycota, five fungal species with coenocytic hyphae were also included. We found that mammalian and plant isolates of Pythium spp. all hydrolysed sucrose, but Lagenidium species and the fungal strains did not. In addition, both Pythium spp. and Lagenidium spp. were found to be maltose-positive, whereas fungal strains did not hydrolyse this sugar. The fungal species and thermo-sensitive Lagenidium giganteum and Lagenidium humanum were urease-negative, but the mammalian Lagenidium spp. and Pythium spp. hydrolysed urea within 24  h. These findings suggest these assays can be used for the presumptive differentiation of mammalian Oomycota species in the laboratory.

Comparative mitochondrial genome analysis of Pythium insidiosum and related oomycete species provides new insights into genetic variation and phylogenetic relationships

Oomycetes are eukaryotic microorganisms, which are phylogenetically distinct from the true-fungi, which they resemble morphologically. While many oomycetes are pathogenic to plants, Pythium insidiosum is capable of infecting humans and animals. Mitochondrial (mt) genomes are valuable genetic resources for exploring the evolution of eukaryotes. During the course of 454-based nuclear genome sequencing, we identified a complete 54.9 kb mt genome sequence, containing 2 large inverted repeats, from P. insidiosum. It contains 65 different genes (including 2 ribosomal RNA genes, 25 transfer RNA genes and 38 genes encoding NADH dehydrogenases, cytochrome b, cytochrome c oxidases, ATP synthases, and ribosomal proteins). Thirty-nine of the 65 genes have two copies, giving a total of 104 genes. A set of 30 conserved protein-coding genes from the mt genomes of P. insidiosum, 11 other oomycetes, and 2 diatoms (outgroup) were used for phylogenetic analyses. The oomycetes can be classified into 2 phylogenetic groups, in relation to their taxonomic lineages: Saprolegnialean and Peronosporalean. P. insidiosum is more closely related to Pythium ultimum than other oomycetes. In conclusion, the complete mt genome of P. insidiosum was successfully sequenced, assembled, and annotated, providing a useful genetic resource for exploring the biology and evolution of P. insidiosum and other oomycetes.

Vascular Pythiosis of the Lower Extremity in Northern Thailand

Pythiosis is a disease caused by Pythium insidiosum, a fungus-like organism. P. insidiosum is pathogenic in mammals, particularly in horses, dogs, and humans. Human pythiosis can be classified into 4 types: (1) cutaneous/subcutaneous, (2) ocular, (3) vascular, and (4) disseminated pythiosis. Vascular pythiosis is a rare disease but a serious limb- and life-threatening infection. We reviewed 22 cases over a 10-year period in Maharaj Nakorn Chiang Mai/Chiang Mai University Hospital. The survival rate was around 63.6% during our follow-up period. The only effective treatment was complete excision of the infected tissue, which was done mainly by major amputation, such as above-knee amputation. This report raises awareness of this disease, which needs preemptive diagnosis and appropriate treatment.

The Immunoreactive Exo-1,3-β-Glucanase from the Pathogenic Oomycete Pythium insidiosum Is Temperature Regulated and Exhibits Glycoside Hydrolase Activity

The oomycete organism, Pythium insidiosum, is the etiologic agent of the life-threatening infectious disease called "pythiosis". Diagnosis and treatment of pythiosis is difficult and challenging. Novel methods for early diagnosis and effective treatment are urgently needed. Recently, we reported a 74-kDa immunodominant protein of P. insidiosum, which could be a diagnostic target, vaccine candidate, and virulence factor. The protein was identified as a putative exo-1,3-ß-glucanase (Exo1). This study reports on genetic, immunological, and biochemical characteristics of Exo1. The full-length exo1 coding sequence (2,229 bases) was cloned. Phylogenetic analysis showed that exo1 is grouped with glucanase-encoding genes of other oomycetes, and is far different from glucanase-encoding genes of fungi. exo1 was up-regulated upon exposure to body temperature, and its gene product is predicted to contain BglC and X8 domains, which are involved in carbohydrate transport, binding, and metabolism. Based on its sequence, Exo1 belongs to the Glycoside Hydrolase family 5 (GH5). Exo1, expressed in E. coli, exhibited ß-glucanase and cellulase activities. Exo1 is a major intracellular immunoreactive protein that can trigger host immune responses during infection. Since GH5 enzyme-encoding genes are not present in human genomes, Exo1 could be a useful target for drug and vaccine development against this pathogen.

Draft Genome Sequence of the Pathogenic Oomycete Pythium insidiosum Strain Pi-S, Isolated from a Patient with Pythiosis

Pythium insidiosum is an oomycete that causes a life-threatening infectious disease called pythiosis in humans and animals living in tropical and subtropical countries. Here, we report the first draft genome sequence of P. insidiosum. The genome of P. insidiosum is 53.2 Mb and contains 14,962 open reading frames.

Pythiosis in sheep from Paraná, southern Brazil

Abstract: This paper reports pythiosis in a sheep from southwestern Paraná, Brazil, confirmed by indirect ELISA (Enzime-Linked Immunosorbent Assay) and immunohistochemistry, as well as it describes the macro and microscopic injuries, in order to understand the pathogenicity. A 4-year-old ewe from a flock of 30 Santa Inês sheep, raised semi-extensively with access to a weir, showed cachexia, bilateral enlargement in nasal region, a serous and bloody secretion with a fetid odor from its nose and swollen submandibular and retropharyngeal lymph nodes. Blood collection was performed trough jugular vein puncture in order to make complete blood cell count (CBC) and to obtain serum for the subsequent serological examination. As the hematological counts were within the normal range for sheep, the animal was euthanized and submitted to necropsy. Indirect ELISA resulted positive for pythiosis. Necropsy revealed necrosis of the hard palate with a diameter of 3.5cm and extending up to the nasal cavity, forming a fistula. Submandibular and retropharyngeal lymph nodes were enlarged and edematous on section. Microscopic findings for submandibular and retropharyngeal lymph nodes consisted in moderate infiltration of eosinophils mainly in the subcapsular sinus, characterizing reactive eosinophilic lymphadenitis. The nasal cavity revealed rhinitis and oral cavity stomatitis with necro-eosinophilic and pronounced multifocal granulomatous infiltration and presence of hyphae. Hyphae found in palate and nasal cavity were positive for Pythium insidiosum by Grocott's method and immunohistochemistry, the last one considered to be confirmatory for the pathogen diagnostic. This report has an important epidemiological aspect, as it is the first case of pythiosis in sheep confirmed by serology in South Brazil and an alert of possible infection by the pathogen in floodplains.

Production of arachidonic and eicosapentaenoic acids by the marine oomycete Halophytophthora

Polyunsaturated fatty acids (PUFAs) are fatty acids with more than one double bond in the chemical structure. Arachidonic acid (ARA, 20:4 (n-6)) and eicosapentaenoic acid (EPA, 22:5 (n-3)) are common PUFAs with beneficial health effects. Marine fish and meat are the main sources of omega-3 and omega-6 fatty acids in human's diet, respectively. In particular, there is a general decline in fish catch, implicating the need for an alternative source of omega-3 fatty acids. Previous studies have examined the production of polyunsaturated fatty acids including ARA and EPA by various microorganisms, including microalgae, fungi, and thraustochytrids. In this study, the production of ARA and EPA by 10 isolates of four estuarine Halophytophthora species (Halophytophthora avicenniae, Halophytophthora polymorphica, Halophytophthora vesicula, and Halophytophthora spinosa var. spinosa) cultured from fallen mangrove leaves in Taiwan was examined. The yield of ARA ranged from 0.004 to 0.052 g/L with the highest yield of ARA obtained from H. spinosa var. spinosa IMB162, but no or a very low level of EPA was produced by IMB162. For EPA production by Halophytophthora spp., the yield ranged from 0 to 0.047 g/L. Percentage of ARA in total fatty acid ranged between 7.16 and 25.02%. One-way ANOVA analysis using Tukey Test (p ≥ 0.05) suggested that there is significant difference in the percentage of EPA in total fatty acid produced by the isolates, which ranged from 0.01 to 18.42%. BODIPY 505/515 fluorescent staining suggests that lipid bodies were evenly distributed in the mycelia of Halophytophthora species.

The elicitin-like glycoprotein, ELI025, is secreted by the pathogenic oomycete Pythium insidiosum and evades host antibody responses

Pythium insidiosum is a unique oomycete that can infect humans and animals. Patients with a P. insidiosum infection (pythiosis) have high rates of morbidity and mortality. The pathogen resists conventional antifungal drugs. Information on the biology and pathogenesis of P. insidiosum is limited. Many pathogens secrete proteins, known as effectors, which can affect the host response and promote the infection process. Elicitins are secretory proteins and are found only in the oomycetes, primarily in Phytophthora and Pythium species. In plant-pathogenic oomycetes, elicitins function as pathogen-associated molecular pattern molecules, sterol carriers, and plant defense stimulators. Recently, we reported a number of elicitin-encoding genes from the P. insidiosum transcriptome. The function of elicitins during human infections is unknown. One of the P. insidiosum elicitin-encoding genes, ELI025, is highly expressed and up-regulated at body temperature. This study aims to characterize the biochemical, immunological, and genetic properties of the elicitin protein, ELI025. A 12.4-kDa recombinant ELI025 protein (rELI025) was expressed in Escherichia coli. Rabbit anti-rELI025 antibodies reacted strongly with the native ELI025 in P. insidiosum’s culture medium. The detected ELI025 had two isoforms: glycosylated and non-glycosylated. ELI025 was not immunoreactive with sera from pythiosis patients. The region near the transcriptional start site of ELI025 contained conserved oomycete core promoter elements. In conclusion, ELI025 is a small, abundant, secreted glycoprotein that evades host antibody responses. ELI025 is a promising candidate for development of diagnostic and therapeutic targets for pythiosis.

Cutaneous, Subcutaneous and Systemic Mycology

The first description of dermatophytosis was recorded by Celsus, a Roman encyclopaedist who described a suppurative infection of scalp (‘porrigo’ or ‘kerion of Celsus’) in De Re Medicina (30 A.D.). Throughout the middle ages, several descriptions of dermatophytosis were produced where it is described as ‘tinea’. The keratin-destroying moths which made circular holes in the woollen garments are known as Tinea. Due to similarity in the structure of circular lesion of dermatophytosis on the smooth skin with the circular hole made by moth, Cassius Felix introduced the term ‘tinea’ to describe the lesions. In 1806, Alibert used the term ‘favus’ to describe the honey-like exudate in some scalp infections. However, the fungal aetiology of tinea was first detected by Robert Remak, a Polish physician who first observed the presence of hyphae in the crusts of favus. This detection is also a landmark in medical history because this is the first description of a microbe causing a human disease. He himself did not publish his work, but he permitted the reference of his observations in a dissertation by Xavier Hube in 1837. Remak gave all the credits of his discovery to his mentor Schoenlein who first published the fungal etiological report of favus in 1839. He observed the infectious nature of the favus by autoinoculation into his own hands and also successfully isolated the fungus later (1945) and named Achorion schoenleinii (Trichophyton schoenleinii) in honour of his mentor. In 1844, Gruby described the etiologic agent of tinea endothrix, later became known as Trichophyton tonsurans. The genus Trichophyton was created and described by Malmsten (1845) with its representative species T. tonsurans. Charles Robin identified T. mentagrophytes in 1847 and T. equinum was identified by Matruchot and Dassonville in 1898. Raymond Jacques Adrien Sabouraud (France) first compiled the description of Trichophyton in his book (Les Teignes) in 1910 which was based on his observation in artificial culture. The sexual state of dermatophyte was described by Nannizzi (1927). Emmons (1934) first reported the classification of dermatophytes based on vegetative structures and conidia. Gentles (1958) established the successful treatment of tinea capitis with griseofulvin.

Imported pythium insidiosum keratitis after a swim in Thailand by a contact lens-wearing traveler

A 30-year-old woman with a history of contact lens wear and exposure to swimming pool water in Thailand presented with a non-responsive, progressive corneal ulcer of the right eye. Confocal microscopy evidenced septate linear branching structures, raising suspicion of fungal keratitis. She was promptly treated with topical antibiotics and both topical and intravenous caspofungin plus voriconazole. Worsening of the clinical picture after 1 month of intensive medical therapy led to a large therapeutic penetrating keratoplasty being performed. Corneal cultures grew a mold-like organism, which was identified by sequencing as Pythium insidiosum, an aquatic oomycete. After 4 years of follow-up, the graft exhibits no infection relapse, but graft transparency has been lost after two rejection episodes. Keratoplasty combined with antifungal treatment may offer a cure to P. insidiosum keratitis, although long-term preservation of corneal transparency is difficult to obtain.

New insights into the in vitro susceptibility of Pythium insidiosum

We have determined the in vitro activity of several antibacterial and antifungal drugs against Pythium insidiosum using broth microdilution (BMD), disk diffusion, and Etest methods. The largest zones of inhibition (disk diffusion) and the lowest BMD and Etest MICs were observed for azithromycin, clarithromycin, linezolid, mupirocin, doxycycline, minocycline, and tigecycline. The in vitro activities observed suggest that antibacterials, which act by inhibiting protein synthesis, are promising candidate therapies for the treatment of pythiosis.

A complicated case of vascular Pythium insidiosum infection treated with limb-sparing surgery

INTRODUCTION

Pythiosis is a serious life- and limb-threatening infection endemic to Thailand, but rarely seen in the Western hemisphere. Here, we present a unique case of vascular pythiosis initially managed with limb-sparing vascular bypass grafts complicated by a pseudoaneurysm in our repair.

PRESENTATION OF CASE

The patient is a 17 year-old Jamaican male with severe aplastic anemia. He sustained a minor injury to his left leg while fishing in Jamaica, which evolved to become an exquisitely tender inguinal swelling. His physical exam and imaging were significant for arteriovenous fistula with limb ischemia. Pathology obtained during surgery for an extra-anatomic vascular bypass showed extensive invasion by Pythium insidiosum. He later developed a pseudoaneurysm at the site of proximal anastomosis and required urgent intervention.

DISCUSSION

This patient presented with a rare, but classic case of vascular pythiosis, which was unrecognized at the time of presentation. A variety of therapeutic modalities have been used to treat this disease, including antibiotics, antifungals, and immunotherapy, but the ultimate management of vascular pythiosis is surgical source control.

CONCLUSION

A high index of suspicion in susceptible patients is needed for timely diagnosis of vascular pythiosis to achieve optimal source control.

Update on pythiosis immunobiology and immunotherapy

Pythiosis is an invasive, ulcerative, pyogranulomatous disease caused by Pythium insidiosum, a fungus-like oomycete that has been reported to affect humans, horses, dogs, and other mammals mainly in tropical and subtropical areas of the world. The disease is characterized by an eosinophilic granulomatous and a Th2 immune response which in turn helps to protect the fungus from the host cells. Pythiosis can present clinically in subcutaneous, gastrointestinal, and vascular tissues or in a systemically disseminated form depending on the species and site of infection. Changes in iron metabolism and anemia are commonly observed. The diagnosis is accomplished through clinical and pathological features, laboratory characteristics of cultures, serological and molecular tests. Treatment includes radical surgery, antimicrobial drugs, immunotherapy or a combination of these treatments. Immunotherapy is a practical and non-invasive alternative for treating pythiosis which is believed to promote a switch from a Th2 to Th1 immune response, resulting in a favorable clinical response. This therapy has demonstrated cure rates above 70% and 55% in horses and humans but low cure rates in dogs and cats. Despite the curative properties of this type of immunotherapy, the antibodies that are produced do not prevent host reinfection. Thus, development of effective adjuvants and new diagnostic techniques for early disease diagnosis are of utmost importance. The aim of this review was to promote pythiosis awareness and to provide an update about the immunotherapy and immunobiology of this disease.

In vitro synergism observed with azithromycin, clarithromycin, minocycline, or tigecycline in association with antifungal agents against Pythium insidiosum

We describe here the in vitro activities of azithromycin, clarithromycin, minocycline, or tigecycline alone and in combination with amphotericin B, itraconazole, terbinafine, voriconazole, anidulafungin, caspofungin, or micafungin against 30 isolates of the oomycete Pythium insidiosum. The assays were based on the CLSI M38-A2 technique and the checkerboard microdilution method. The main synergisms observed were through the combination of minocycline with amphotericin B (73.33%), itraconazole (70%), and micafungin (70%) and of clarithromycin with micafungin (73.33%).

The Capnocytophaga canimorsus isolate that caused sepsis in an immunosufficient man was transmitted by the large pine weevil Hylobius abietis

The first vector-borne Capnocytophaga canimorsus sepsis case is presented. An immunocompetent male who denied any contact with canines and who worked in a sawmill was bitten on his neck by a large pine weevil (Hylobius abietis L.; Coleoptera: Curculionidae). Bacteriological diagnosis was confirmed by 16S rRNA gene sequence analysis.

Cutaneous pythiosis in two dogs from Wisconsin, USA

BACKGROUND

Pythium insidiosum is an oomycete that causes cutaneous lesions or infiltrative gastrointestinal disease in dogs, cats, humans, horses and other mammals, primarily in tropical and subtropical climates.

HYPOTHESIS/OBJECTIVES

We report the clinicopathological findings associated with cutaneous pythiosis in two dogs from a Northern temperate climate zone.

ANIMALS

A 3-year-old intact male Chesapeake Bay retriever was presented with an ulcerated soft-tissue swelling over the left eye. A 4-year-old spayed female German shepherd dog was presented with a soft-tissue swelling overlying the right hock. Both dogs lived in northern latitudes (between 43 and 45°N) and neither had travelled outside of Wisconsin or Michigan's upper peninsula, USA.

METHODS

Histopathological examination and culture of affected tissues on specialized media, serology for anti-P. insidiosum antibodies, P. insidiosum-specific PCR and ribosomal RNA gene sequencing were carried out.

RESULTS

Histopathological examination revealed pyogranulomatous and eosinophilic inflammation associated with wide, poorly septate hyphae.

CONCLUSIONS AND CLINICAL IMPORTANCE

Even clinicians who practice in temperate climates should consider pythiosis as a differential diagnosis for young to middle-aged adult dogs presented with ulcerated cutaneous nodules or infiltrative gastrointestinal disease.

In vitro reproduction of the life cycle of Pythium insidiosum from kunkers' equine and their role in the epidemiology of pythiosis

Pythium insidiosum is an important pathogen of mammals' species, including humans. Equine is the main species affected by this oomycete. P. insidiosum requires an aquatic environment to develop its life cycle, and the susceptible hosts are contaminated when they contact the microorganism in swampy areas. The equine pythiosis is characterized by the formation of irregular masses within the cutaneous lesions, called kunkers, which easily detach from the lesion. From these structures, it is possible to isolate P. insidiosum in pure cultures. The present study aimed to reproduce in vitro the life cycle of P. insidiosum from kunkers of equine clinical lesions. Fifteen kunkers from different horses were tested. It was observed that the discharge of zoospores occurred after 24-48 h of incubation at 37 °C in, respectively, 40 and 47 % of the kunkers evaluated. Only two samples showed no development of the asexual cycle of P. insidiosum under the conditions tested. It was possible to demonstrate that kunkers are able to restart the asexual cycle of P. insidiosum. Based on our in vitro results, we highlight the importance of these structures in the epidemiology of the pythiosis, since kunkers can be a potential source of contamination of this oomycete for aquatic environments.

Canine gastrointestinal pythiosis treatment by combined antifungal and immunotherapy and review of published studies

Pythium insidiosum is an oomycete, a fungal like microorganism, which infects mammals, causing pythiosis in animals and humans, especially in tropical and subtropical regions around the world. The treatment for this infection is very difficult, and therapeutic options commonly comprise surgery, immunotherapy and antimicrobial drugs. The present report describes the clinical healing of a dog with gastrointestinal pythiosis by treatment with a combination of antifungals and immunotherapy, as well as reviews the cases reported in the literature that used some type of therapy for canine pythiosis. A 2.5-year-old male beagle initially showed sporadic vomiting episodes, and this symptom became more frequent 5 months after the onset of clinical signs. Celiotomy procedure found thickness of the stomach wall extending to the pylorus and duodenum. A biopsy was performed, and the diagnosis of pythiosis was made by mycological, histopathological analyses and molecular identification. Therapy was based on an association of terbinafine plus itraconazole during 12 months and immunotherapy for 2.5 months. The healing of the dog reported here allows us to propose the use of immunotherapy associated with antifungal therapy to treat canine gastrointestinal pythiosis. However, additional studies should be performed on a larger number of patients to establish a standard treatment protocol for canine pythiosis.

The safety assessment of Pythium irregulare as a producer of biomass and eicosapentaenoic acid for use in dietary supplements and food ingredients

Polyunsaturated fatty acids, docosahexaenoic acid (DHA, 22:6, n-3), eicosapentaenoic acid (EPA, 20:5, n-3), and arachidonic acid (ARA, 20:4 n-6), have multiple beneficial effects on human health and can be used as an important ingredient in dietary supplements, food, feed and pharmaceuticals. A variety of microorganisms has been used for commercial production of these fatty acids. The microorganisms in the Pythium family, particularly Pythium irregulare, are potential EPA producers. The aim of this work is to provide a safety assessment of P. irregulare so that the EPA derived from this species can be potentially used in various commercial applications. The genus Pythium has been widely recognized as a plant pathogen by infecting roots and colonizing the vascular tissues of various plants such as soybeans, corn and various vegetables. However, the majority of the Pythium species (including P. irregulare) have not been reported to infect mammals including humans. The only species among the Pythium family that infects mammals is P. insidiosum. There also have been no reports showing P. irregulare to contain mycotoxins or cause potentially allergenic responses in humans. Based on the safety assessment, we conclude that P. irregulare can be considered a safe source of biomass and EPA-containing oil for use as ingredients in dietary supplements, food, feed and pharmaceuticals.

Outbreak of Pythium keratitis during rainy season: a case series

PURPOSE

To describe typical clinical and laboratory characteristics of severe fungal keratitis caused by Pythium insidiosum during the rainy season in Northeast Thailand and to report the efficacy of P. insidiosum vaccine in the treatment of Pythium keratitis.

METHODS

A series of hospital-based consecutive cases of Pythium keratitis were diagnosed and treated at Srinagarind Hospital (Khon Kaen University, Khon Kaen, Thailand). The clinical presentations, diagnostic tests, and management are described.

RESULTS

Severe fungal keratitis caused by P. insidiosum was diagnosed in 5 eyes of 4 patients between May 2009 and July 2009. All cases had a history of fungal keratitis after being exposed to contaminated water. Upon slit-lamp examination, subepithelial and superficial stromal opacities were observed in a reticular pattern in all cases. Pythium insidiosum was identified and confirmed by both microbiological culture and polymerase chain reaction. Clinical worsening was detected after conventional treatment with antifungal agents. Therapeutic penetrating keratoplasty with either donor cornea or scleral graft was performed together with topical antifungal administration and P. insidiosum vaccination. Subsequent evisceration was performed in 1 eye.

CONCLUSIONS

An outbreak of Pythium keratitis in Northeast Thailand was reported. Distinctive clinical features are a suggestive clue for early diagnosis. Combination treatment including topical antifungal agents, radical surgery, and P. insidiosum vaccine may be considered for the management of Pythium keratitis.

Immunodetection of fungal and oomycete pathogens: established and emerging threats to human health, animal welfare and global food security

Filamentous fungi (moulds), yeast-like fungi, and oomycetes cause life-threatening infections of humans and animals and are a major constraint to global food security, constituting a significant economic burden to both agriculture and medicine. As well as causing localized or systemic infections, certain species are potent producers of allergens and toxins that exacerbate respiratory diseases or cause cancer and organ damage. We review the pathogenic and toxigenic organisms that are etiologic agents of both animal and plant diseases or that have recently emerged as serious pathogens of immunocompromised individuals. The use of hybridoma and phage display technologies and their success in generating monoclonal antibodies for the detection and control of fungal and oomycete pathogens are explored. Monoclonal antibodies hold enormous potential for the development of rapid and specific tests for the diagnosis of human mycoses, however, unlike plant pathology, their use in medical mycology remains to be fully exploited.