Visualization of Arbuscular Mycorrhizal Fungal Extraradical Hyphae and Spores Vitality and Activity.

The hyphae and spores of arbuscular mycorrhizal (AM) fungi represent an essential component in the extraradical zone due to their role in nutrients and water uptake and as propagules that allow the perpetuation of the AM symbiosis over time, respectively. However, the attention of scientific literature is usually more focused on root colonization than on the study of the extraradical components of AM fungi, especially their vital, active, or functional fractions. This chapter presents some easy-to-use alternatives for staining vital, active, or functional structures of AM fungi for their subsequent microscopic visualization, such as the application of enzyme-based stains, NADPH formation, and also nucleus staining. Some modified methods for the extraction of mycelium from the soil are also presented.

Protein extract from Cereus jamacaru (DC.) inhibits Colletotrichum gloeosporioides growth by stimulating ROS generation and promoting severe cell membrane damage.

Mandacaru (Cereus jamacaru DC.), is a cactaceous symbol of caatinga vegetation at Brazilian Northeast region, however, there are no much studies about biochemical properties of this species. Here, the pioneering study brings very relevant data to highlight the importance of research with endemic plants of the caatinga. Afterward, the presence of enzymes such as peroxidase, protease, chitinase, ß-1,3-glucanase, and serine (trypsin) and cysteine (papain) protease inhibitors were evaluated. The peroxidase activity was higher in roots than other tissues. The ß-1,3-glucanase and proteolytic activity were prominent in stem and roots. The chitinase activity and protease inhibitor for both classes analyzed were detected in the stem and fruit peel. Antifungal activity against Colletotrichum gloeosporioides showed the root extract has a promising inhibitory activity on this economical important phytopathogenic fungus. After the contact of the hyphae with root extract increase in membrane permeability, based on Propidium Iodide (PI) uptake, and production of reactive oxygen species (ROS) were detected, compared to negative control. In addition, Scanning Electron Microscopy (SEM) analysis showed morphological damage on hyphae structure indicating that the treatment debilitates either cell membrane or cell wall leading to the cell death C. gloeosporioides.

In vitro anti-Pythium insidiosum activity of biogenic silver nanoparticles.

Pythium insidiosum belongs to the phylum Oomycota. It is capable of infecting mammals causing a serious condition called pythiosis, which affects mainly horses in Brazil and humans in Thailand. The objective of the present study was to verify the in vitro anti-P. insidiosum activity of a biogenic silver nanoparticle (bio-AgNP) formulation. The in vitro assays were evaluated on P. insidiosum isolates (n = 38) following the M38-A2 protocol. Damage to the P. insidiosum hyphae ultrastructure was verified by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Bio-AgNP inhibition concentrations on P. insidiosum isolates ranged from 0.06 to 0.47 µg/ml. It was observed through SEM that P. insidiosum hyphae treated showed surface roughness, as well as cell walls with multiple retraction areas, loss of continuity, and rupture in some areas. The TEM of treated hyphae did not differentiate organelle structures; also, the cellular wall was rarefied, showing wrinkled and partly ruptured borders. The bio-AgNP evaluated has excellent in vitro anti-P. insidiosum activity. However, further studies on its in vivo action are necessary as so to determine the possibility of its use in the treatment of the disease in affected hosts.

Automated, continuous video microscopy tracking of hyphal growth.

The growth of filamentous fungi is a complex process that involves hyphal elongation and branching. Microscopic observations provide a wealth of information on fungal growth, although often requiring laborious manual intervention to record and analyze images. Here, we introduce a novel tool for automated tracking of growth in fungal hyphae that affords quantitative analysis of growth rate and morphology. We supplied a student-grade bright field microscope with stepper motors to enable computer-control of the microscope stage. In addition, we developed an image-processing routine that detects in real-time the tip of a hypha and tracks it as the hypha elongates. To achieve continuous observation of hyphal growth, our system automatically maintains the observed sample within field-of-view and performs periodic autofocus correction in the microscope. We demonstrate automated, continuous tracking of hyphal growth in Trichoderma atroviride with sampling rates of seconds and observation times of up to 14 h. Tracking records allowed us to determine that T. atroviride hyphae grow with characteristic elongation rates of ∼70 nm/s. Surprisingly, we found that prior to the occurrence of an apical branching event the parental hypha stopped growing during a few minutes. These arrest events presented occasionally for subapical branching as well. Finally, from tracking data we found that the persistence length (a measure of filament extension before presenting a change in direction) associated to T. atroviride hyphae is 362 µm. Altogether, these results show how integration of image analysis and computer control enable quantitative microscopic observations of fungal hyphae dynamics.

Impact of Cationic and Neutral Gemini Surfactants on Conidia and Hyphal Forms of Aspergillus brasiliensis.

This study investigates the biological activity of two cationic gemini surfactants, hexamethylene-1,6-bis-(N,N-dimethyl-N-dodecylammonium bromide) C6 and pentamethylene-1,5-bis-(N,N-dimethyl-N-dodecyla,.mmonium bromide) C5, and their two neutral analogs, hexamethylene-1,6-bis-(N-methyl-N-dodecylamine) (A6) and pentamethylene-1,5-bis-(N-methyl-N-dodecylamine) (A5). Experiments were performed with Aspergillus brasiliensis, which is used in the standard tests for biocides. The minimal inhibitory concentration (MIC) values for conidia and mycelium were determined using the dilution method. The viability of the conidia was evaluated using the plate count method. The dry mass of the mycelium was determined using the thermogravimetric method. Ergosterol was extracted from the mycelium and evaluated by gas chromatography. The effect of gemini surfactants on fungal morphology was observed using scanning electron microscopy. Cationic gemini surfactants were found to be active at lower concentrations compared to their non-ionic analogues, rapidly reducing the total number of conidia that were able to grow. They also decreased both the ergosterol content in the mycelium and its dry weight. These results suggest that cationic gemini surfactants C6 and C5 could have a wide range of practical applications as active compounds. However, it should be remembered that usage at too low concentrations, below the MIC, will only lead to short-term disturbances in the development of conidia and mycelium.

Amycolatopsis vastitatis sp. nov., an isolate from a high altitude subsurface soil on Cerro Chajnantor, northern Chile.

The taxonomic position of a novel Amycolatopsis strain isolated from a high altitude Atacama Desert subsurface soil was established using a polyphasic approach. The strain, isolate H5T, was shown to have chemical properties typical of members of the genus Amycolatopsis such as meso-diaminopimelic acid as the diamino acid in the cell wall peptidoglycan, arabinose and galactose as diagnostic sugars and MK-9(H4) as the predominant isoprenologue. It also has cultural and morphological properties consistent with its classification in the genus, notably the formation of branching substrate hyphae which fragment into rod-like elements. 16S rRNA gene sequence analyses showed that the strain is closely related to the type strain of Amycolatopsis mediterranei but could be distinguished from this and other related Amycolatopsis strains using a broad range of phenotypic properties. It was separated readily from the type strain of Amycolatopsis balhymycina, its near phylogenetic neighbour, based on multi-locus sequence data, by low average nucleotide identity (92.9%) and in silico DNA/DNA relatedness values (51.3%) calculated from draft genome assemblies. Consequently, the strain is considered to represent a novel species of Amycolatopsis for which the name Amycolatopsis vastitatis sp. nov. is proposed. The type strain is H5T (= NCIMB 14970T = NRRL B-65279T).

Surface imaging of the filamentous fungus Penicillium simplicissimum growing in a solid-state fermentation system.

A comparative study on the lipase-producing fungus Penicillium simplissicimum, grown on a tray type solid-state fermentation (SSF) bioreactor, was performed using stereoscopy, focus Z-stacking stereoscopic images, field emission scanning electron microscopy (FE-SEM) and environmental scanning electron microscopy (ESEM) to better characterize the morphology of filamentous fungi in SSF and their distribution over the solid matrix. The imaging of live fungal samples using a stereomicroscope with focus Z-stacking showed differences in colonization between a static SSF and an intermittent agitated SSF. A comparison of the stereomicroscopy, hi-vacuum and environmental scanning electron microscopy results obtained using different protocols for sample processing showed that fixation with osmium tetroxide vapor and subsequent hydrated imaging is the best combination of sample preparation and imaging conditions for keeping the arrangement of the aerial hyphae and conidia morphology closer to the natural state. These combined methodologies can be applied in the SSF of fungal growth to characterize the formation of conidiophores over time, the conidia morphology and the spatial organization after their release from conidiophores. Mycelium colonization over the matrix, which is an important characteristic related to the production of different biotechnological products, could be observed and provide more knowledge about fungal physiology behavior during SSF.

Sugarcane smut: shedding light on the development of the whip-shaped sorus.

Background and Aims: Sugarcane smut is caused by the fungus Sporisorium scitamineum (Ustilaginales/Ustilaginomycotina/Basidiomycota), which is responsible for losses in sugarcane production worldwide. Infected plants show a profound metabolic modification resulting in the development of a whip-shaped structure (sorus) composed of a mixture of plant tissues and fungal hyphae. Within this structure, ustilospores develop and disseminate the disease. Despite the importance of this disease, a detailed histopathological analysis of the plant-pathogen interaction is lacking. Methods: The whip-shaped sorus was investigated using light microscopy, scanning and transmission electron microscopy, histochemical tests and epifluorescence microscopy coupled with deconvolution. Key Results: Sorus growth is mediated by intercalary meristem activity at the base of the sorus, where the fungus causes partial host cell wall degradation and formation of intercellular spaces. Sporogenesis in S. scitamineum is thallic, with ustilospore initials in intercalary or terminal positions, and mostly restricted to the base of the sorus. Ustilospore maturation is centrifugal in relation to the ground parenchyma and occurs throughout the sorus median region. At the apex of the sorus, the fungus produces sterile cells and promotes host cell detachment. Hyphae are present throughout the central axis of the sorus (columella). The plant cell produces callose around the intracellular hyphae as well as inside the papillae at the infection site. Conclusions: The ontogeny of the whip-shaped sorus suggests that the fungus can cause the acropetal growth in the intercalary meristem. The sporogenesis of S. scitamineum was described in detail, demonstrating that the spores are formed exclusively at the base of the whip. Light was also shed on the nature of the sterile cells. The presence of the fungus alters the host cell wall composition, promotes its degradation and causes the release of some peripheral cells of the sorus. Finally, callose was observed around fungal hyphae in infected cells, suggesting that deposition of callose by the host may act as a structural response to fungal infection.

[Fungal biomass estimation in soils from southwestern Buenos Aires province (Argentina) using calcofluor white stain]. / Estimación de la biomasa fúngica en un suelo del sudoeste de la provincia de Buenos Aires (Argentina) con una tinción directa con blanco de calcoflúor.

Soil microorganisms are vital for ecosystem functioning because of the role they play in soil nutrient cycling. Agricultural practices and the intensification of land use have a negative effect on microbial activities and fungal biomass has been widely used as an indicator of soil health. The aim of this study was to analyze fungal biomass in soils from southwestern Buenos Aires province using direct fluorescent staining and to contribute to its use as an indicator of environmental changes in the ecosystem as well as to define its sensitivity to weather conditions. Soil samples were collected during two consecutive years. Soil smears were prepared and stained with two different concentrations of calcofluor, and the fungal biomass was estimated under an epifluorescence microscope. Soil fungal biomass varied between 2.23 and 26.89µg fungal C/g soil, being these values in the range expected for the studied soil type. The fungal biomass was positively related to temperature and precipitations. The methodology used was reliable, standardized and sensitive to weather conditions. The results of this study contribute information to evaluate fungal biomass in different soil types and support its use as an indicator of soil health for analyzing the impact of different agricultural practices.

Localization and role of MYO-1, an endocytic protein in hyphae of Neurospora crassa.

The subapical endocytic collar is a prominent feature of hyphae of Neurospora crassa. It comprises a dynamic collection of actin patches associated with a number of proteins required for endocytosis, namely, ARP-2/3 complex, fimbrin, coronin, etc. We presently show that MYO-1 is another key component of this endocytic collar. A myo-1 sequence was identified in the genome of N. crassa and used it to generate a strain with a myo-1-sgfp allele under the ccg1 promoter. Examination of living hyphae by confocal microscopy, revealed MYO-1-GFP located mainly as a dynamic collection of small patches arranged in collar-like fashion in the hyphal subapex. Dual tagging showed MYO-1-GFP partially colocalized with two other endocytic proteins, fimbrin and coronin. MYO-1 was also present during septum formation. By recovering a viable strain, albeit severely inhibited, after deletion of myo-1, it was possible to investigate the phenotypic consequences of the elimination of MYO-1. Deletion of myo-1 caused a severe reduction in growth rate (95%), near absence of aerial mycelium and no conidiation. A reduced uptake of the lipophilic dye FM4-64 indicated a deficiency in endocytosis in the Δmyo-1 mutant. Hyphae were produced by the Δmyo-1 mutant but their morphogenesis was severely affected; hyphal morphology was distorted displaying irregular periods of isotropic and polarized growth. The morphological alterations were accompanied, and presumably caused, by a disruption in the organization and dynamics of a myosin-deprived actin cytoskeleton that, ultimately, compromised the stability and function of the Spitzenkörper as a vesicle supply center.

Effect of fungicide on Fusarium verticillioides mycelial morphology and fumonisin B1 production.

The effect of fludioxonil + metalaxyl-M on the mycelial morphology, sporulation and fumonisin B 1 production by Fusarium verticillioides 103 F was evaluated. Scanning electron microscopy analysis showed that the fungicide caused inhibition of hyphal growth and defects on hyphae morphology such as cell wall disruption, withered hyphae, and excessive septation. In addition, extracellular material around the hyphae was rarely observed in the presence of fludioxonil + metalaxyl-M. While promoting the reduction of mycelial growth, the fungicide increased sporulation of F. verticillioides compared to the control, and the highest production occurred on the 14 (th) day in the treatments and on the 10 (th) day in the control cultures. Fumonisin B 1 production in the culture media containing the fungicide (treatment) was detected from the 7 (th) day incubation, whereas in cultures without fungicide (control) it was detected on the 10 (th) day. The highest fumonisin B 1 production occurred on the 14 (th) day, both for the control and for the treatment. Fludioxonil + metalaxyl - M can interfere in F. verticillioides mycelial morphology and sporulation and increase fumonisin B 1 levels. These data indicate the importance of understanding the effects of fungicide to minimize the occurrence of toxigenic fungi and fumonisins.

Ascosphaera apis, the entomopathogenic fungus affecting larvae of native bees (Xylocopa augusti): First report in South America.

BACKGROUND: Nowadays several invertebrate pollinators of crops and wild plants are in decline as result of multiple and, sometimes, unknown factors; among them, the modern agricultural practices, pests and diseases are postulated as the most important factors. Bees of the genus Xylocopa are considered effective pollinators of passion fruit crops in tropical regions, as well as important pollinators in wild plants, but these bees are attacked by several pathogens that affect different stages in their life cycle. The fungal species of the genus Ascosphaera are commonly associated with social and solitary bee larvae causing chalkbrood disease. AIMS: The aim of the present study was to demonstrate the presence of Ascosphaera apis affecting larvae of Xylocopa augusti in South America. METHODS: For this purpose, A. apis was isolated from affected larvae in YGPSA medium. Final identification was run out by three techniques: (1) Microscopic examination of the hyphae and sizes of the fruiting bodies; (2) Mating test, and specific sexual compatibility test, and (3) PCR detection, using specific primers. RESULTS: This study demonstrates for the first time the presence of A. apis affecting larvae of X. augusti in South America. CONCLUSIONS: The evidence of A. apis affecting the larvae of X. augusti, and the fact that the sharing of pathogens between different bee species has been underestimated, suggests the need for further epidemiological studies in order to determine not only the prevalence of this pathogen among wild pollinators, but also its relationship to the sudden collapse of honey bee colonies in this region.

Effect of fungicide on Fusarium verticillioides mycelial morphology and fumonisin B1 production

The effect of fludioxonil + metalaxyl-M on the mycelial morphology, sporulation and fumonisin B1 production by Fusarium verticillioides 103 F was evaluated. Scanning electron microscopy analysis showed that the fungicide caused inhibition of hyphal growth and defects on hyphae morphology such as cell wall disruption, withered hyphae, and excessive septation. In addition, extracellular material around the hyphae was rarely observed in the presence of fludioxonil + metalaxyl-M. While promoting the reduction of mycelial growth, the fungicide increased sporulation of F. verticillioides compared to the control, and the highest production occurred on the 14th day in the treatments and on the 10th day in the control cultures. Fumonisin B1 production in the culture media containing the fungicide (treatment) was detected from the 7th day incubation, whereas in cultures without fungicide (control) it was detected on the 10th day. The highest fumonisin B1 production occurred on the 14th day, both for the control and for the treatment. Fludioxonil + metalaxyl - M can interfere in F. verticillioides mycelial morphology and sporulation and increase fumonisin B1 levels. These data indicate the importance of understanding the effects of fungicide to minimize the occurrence of toxigenic fungi and fumonisins.

Antibiosis interaction of Staphylococccus aureus on Aspergillus fumigatus assessed in vitro by mixed biofilm formation.

BACKGROUND: Microorganisms of different species interact in several ecological niches, even causing infection. During the infectious process, a biofilm of single or multispecies can develop. Aspergillus fumigatus and Staphyloccocus aureus are etiologic agents that can cause infectious keratitis. We analyzed in vitro single A. fumigatus and S. aureus, and mixed A. fumigatus-S. aureus biofilms. Both isolates were from patients with infectious keratitis. Structure of the biofilms was analyzed through microscopic techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), confocal, and fluorescence microscopy (CLSM) in mixed biofilm as compared with the single A. fumigatus biofilm. RESULTS: To our knowledge, this is the first time that the structural characteristics of the mixed biofilm A. fumigatus-A. fumigatus were described and shown. S. aureus sharply inhibited the development of biofilm formed by A. fumigatus, regardless of the stage of biofilm formation and bacterial inoculum. Antibiosis effect of bacterium on fungus was as follows: scarce production of A. fumigatus biofilm; disorganized fungal structures; abortive hyphae; and limited hyphal growth; while conidia also were scarce, have modifications in their surface and presented lyses. Antagonist effect did not depend on bacterial concentration, which could probably be due to cell-cell contact interactions and release of bacterial products. In addition, we present images about the co-localization of polysaccharides (glucans, mannans, and chitin), and DNA that form the extracellular matrix (ECM). In contrast, single biofilms showed extremely organized structures: A. fumigatus showed abundant hyphal growth, hyphal anastomosis, and channels, as well as some conidia, and ECM. S. aureus showed microcolonies and cell-to-cell bridges and ECM. CONCLUSIONS: Herein we described the antibiosis relationship of S. aureus against A. fumigatus during in vitro biofilm formation, and report the composition of the ECM formed.

Effect of fungicide on Fusarium verticillioides mycelial morphology and fumonisin B1 production

The effect of fludioxonil + metalaxyl-M on the mycelial morphology, sporulation and fumonisin B1 production by Fusarium verticillioides 103 F was evaluated. Scanning electron microscopy analysis showed that the fungicide caused inhibition of hyphal growth and defects on hyphae morphology such as cell wall disruption, withered hyphae, and excessive septation. In addition, extracellular material around the hyphae was rarely observed in the presence of fludioxonil + metalaxyl-M. While promoting the reduction of mycelial growth, the fungicide increased sporulation of F. verticillioides compared to the control, and the highest production occurred on the 14th day in the treatments and on the 10th day in the control cultures. Fumonisin B1 production in the culture media containing the fungicide (treatment) was detected from the 7th day incubation, whereas in cultures without fungicide (control) it was detected on the 10th day. The highest fumonisin B1 production occurred on the 14th day, both for the control and for the treatment. Fludioxonil + metalaxyl - M can interfere in F. verticillioides mycelial morphology and sporulation and increase fumonisin B1 levels. These data indicate the importance of understanding the effects of fungicide to minimize the occurrence of toxigenic fungi and fumonisins.(AU)

Dissecting the function of the different chitin synthases in vegetative growth and sexual development in Neurospora crassa.

Chitin, one of the most important carbohydrates of the fungal cell wall, is synthesized by chitin synthases (CHS). Seven sequences encoding CHSs have been identified in the genome of Neurospora crassa. Previously, CHS-1, -3 and -6 were found at the Spitzenkörper(Spk) core and developing septa. We investigated the functional importance of each CHS in growth and development of N. crassa. The cellular distribution of each CHS tagged with fluorescent proteins and the impact of corresponding gene deletions on vegetative growth and sexual development were compared. CHS-2, -4, -5 and -7 were also found at the core of the Spk and in forming septa in vegetative hyphae. As the septum ring developed, CHS-2-GFP remained at the growing edge of the septum until it localized around the septal pore. In addition, all CHSs were located in cross-walls of conidiophores. A partial co-localization of CHS-1-m and CHS-5-GFP or CHS-2-GFP occurred in the Spk and septa. Analyses of deletion mutants suggested that CHS-6 has a role primarily in hyphal extension and ascospore formation, CHS-5 in aerial hyphae, conidia and ascospore formation, CHS-3 in perithecia development and CHS-7 in all of the aforementioned. We show that chs-7/csmB fulfills a sexual function and chs-6/chsG fulfills a vegetative growth function in N. crassa but not in Aspergillus nidulans, whereas vice versa chs-2/chsA fulfills a sexual function in A. nidulans but not in N. crassa. This suggests that different classes of CHSs can fulfill distinct developmental functions in various fungi. Immunoprecipitation followed by mass spectrometry of CHS-1-GFP, CHS-4-GFP and CHS-5-GFP identified distinct putative interacting proteins for each CHS. Collectively, our results suggest that there are distinct populations of chitosomes, each carrying specific CHSs, with particular roles during different developmental stages.

Pitiose canina: uma doença despercebida na clínica de pequenos animais / Canine pythiosis: an unnoticed disease in the small animal clinic

A pitiose é uma doença granulomatosa decorrente da infecção pelo oomiceto Pythium insidiosum. Essa enfermidade tem recebido grande atenção devido à ampla distribuição do patógeno, sintomatologia variável, dificuldade no diagnóstico e necessidade de seleção de uma terapia apropriada. O presente trabalho objetivou realizar uma revisão de literatura a respeito da pitiose na espécie canina, alertando o médicoveterinário em considerar tal enfermidade na rotina da clínica de pequenos animais. Para a manutenção do ciclo no ambiente, o P. insidiosum necessita de umidade e com temperatura elevada. Não se verifica transmissão direta entre animais ou zoonótica. No Brasil há um considerável volume de estudos da pitiose em cães,principalmente nas regiões Sul e Sudeste. Frequentemente os animais afetados são machos, de grande porte, com idade inferior a três anos. Essa doença Apresenta-se sob as formas gastrintestinal e cutânea, sendo a primeira a mais frequente. A avaliação histopatológica pode representar a única ferramenta para o diagnóstico, poisrotineiramente as amostras encontram-se fixadas em formol, o que inviabiliza o seu envio para a cultura. Asterapias utilizadas apresentam resultados variados e incluem combinação de antifúngicos sistêmicos, cirurgia e imunoterapia. Torna-se essencial a inclusão da pitiose na diferenciação de determinadas enfermidades cutâneas e/ou gastroentéricas que acometem os cães. Essa doença infecciosa não deve ser considerada incomum na práticada clínica veterinária, pois o que provavelmente ocorre é um subdiagnóstico, seja pela ausência de suspeita clínica ou a falta de direcionamento das amostras teciduais para laboratórios especializados

Pythiosis is a granulomatous infectious disease caused by the oomycete Pythium insidiosum. This disease has received great attention due to the pathogen wide distribution, variable symptoms, difficulty in clinical diagnosis and need for appropriate therapy selection. This study aimed to perform a literature review about the pythiosis in dogs, prompting a veterinarian to consider this disease in the small animal clinic routine. For the maintenance of the cycle in the environment, P. insidiosum requires water accumulation and high temperature. There is neither direct transmission among animals nor zoonotic. In Brazil, there is a considerable amount of study on pythiosis in dogs, especially in the South and Southeast regions. Often affected animals are male, large, and below three years of age. The disease shows up under the gastrointestinal and in skin forms, being the first the most common. Histopathology may represent the only tool for the diagnosis, since samples are routinely fixed in formalin, making their culture unfeasible. The therapies used have varied results and include systemic antifungal drug combination, surgery, and immunotherapy. Pythiosis should be included in the differentiation of certain skin and/or gastroenteric ailments that affect dogs. This infectious disease should not be considered unusual in the veterinary clinic practice. What may really occur is an underdiagnosis either by absence of clinical suspicion or lack of direction of the tissue samples to specialized laboratories

Pitiose canina: uma doença despercebida na clínica de pequenos animais / Canine pythiosis: an unnoticed disease in the small animal clinic

A pitiose é uma doença granulomatosa decorrente da infecção pelo oomiceto Pythium insidiosum. Essa enfermidade tem recebido grande atenção devido à ampla distribuição do patógeno, sintomatologia variável, dificuldade no diagnóstico e necessidade de seleção de uma terapia apropriada. O presente trabalho objetivou realizar uma revisão de literatura a respeito da pitiose na espécie canina, alertando o médicoveterinário em considerar tal enfermidade na rotina da clínica de pequenos animais. Para a manutenção do ciclo no ambiente, o P. insidiosum necessita de umidade e com temperatura elevada. Não se verifica transmissão direta entre animais ou zoonótica. No Brasil há um considerável volume de estudos da pitiose em cães,principalmente nas regiões Sul e Sudeste. Frequentemente os animais afetados são machos, de grande porte, com idade inferior a três anos. Essa doença Apresenta-se sob as formas gastrintestinal e cutânea, sendo a primeira a mais frequente. A avaliação histopatológica pode representar a única ferramenta para o diagnóstico, poisrotineiramente as amostras encontram-se fixadas em formol, o que inviabiliza o seu envio para a cultura. Asterapias utilizadas apresentam resultados variados e incluem combinação de antifúngicos sistêmicos, cirurgia e imunoterapia. Torna-se essencial a inclusão da pitiose na diferenciação de determinadas enfermidades cutâneas e/ou gastroentéricas que acometem os cães. Essa doença infecciosa não deve ser considerada incomum na práticada clínica veterinária, pois o que provavelmente ocorre é um subdiagnóstico, seja pela ausência de suspeita clínica ou a falta de direcionamento das amostras teciduais para laboratórios especializados(AU)

Pythiosis is a granulomatous infectious disease caused by the oomycete Pythium insidiosum. This disease has received great attention due to the pathogen wide distribution, variable symptoms, difficulty in clinical diagnosis and need for appropriate therapy selection. This study aimed to perform a literature review about the pythiosis in dogs, prompting a veterinarian to consider this disease in the small animal clinic routine. For the maintenance of the cycle in the environment, P. insidiosum requires water accumulation and high temperature. There is neither direct transmission among animals nor zoonotic. In Brazil, there is a considerable amount of study on pythiosis in dogs, especially in the South and Southeast regions. Often affected animals are male, large, and below three years of age. The disease shows up under the gastrointestinal and in skin forms, being the first the most common. Histopathology may represent the only tool for the diagnosis, since samples are routinely fixed in formalin, making their culture unfeasible. The therapies used have varied results and include systemic antifungal drug combination, surgery, and immunotherapy. Pythiosis should be included in the differentiation of certain skin and/or gastroenteric ailments that affect dogs. This infectious disease should not be considered unusual in the veterinary clinic practice. What may really occur is an underdiagnosis either by absence of clinical suspicion or lack of direction of the tissue samples to specialized laboratories(AU)