Multi-locus sequencing typing reveals geographically related intraspecies variability of Sporothrix brasiliensis.

Sporotrichosis is a subcutaneous mycosis caused by pathogenic Sporothrix species. Among them, Sporothrix brasiliensis is the main species associated with endemic regions in South America, especially Brazil. It is highly virulent and can be spread through zoonotic transmission. Molecular epidemiological surveys are needed to determine the extent of genetic variation, to investigate outbreaks, and to identify genotypes associated with antifungal resistance and susceptibility. This study investigated the sequence variation of different constitutive genes and established a novel multilocus sequence typing (MLST) scheme for S. brasiliensis. Specific primers were designed for 16 genes using Primer-BLAST software based on the genome sequences of three S. brasiliensis strains (ATCC MYA-4823, A001 and A005). Ninety-one human, animal, and environmental S. brasiliensis isolates from different Brazilian geographic regions (South, Southeast, Midwest and Northeast) andtwo isolates from Paraguay were sequenced. The loci that presented the highest nucleotide diversity (π) were selected for the MLST scheme. Among the 16 studied genetic loci, four presented increased π value and were able to distinguish all S. brasiliensis isolates into seven distinct haplotypes. The PCR conditions were standardized for four loci. Some of the obtained haplotypes were associated with the geographic origin of the strains. This study presents an important advance in the understanding of this important agent of sporotrichosis in Brazil. It significantly increased the discriminatory power for genotyping of S. brasiliensis isolates, and enabled new contributions to the epidemiological studies of this human and animal pathogen in Brazil and in other countries.

Sporothrix brasiliensis-specific polymerase chain reaction for the diagnosis of cat and human sporotrichosis through non-invasive samples.

Zoonotic sporotrichosis caused by Sporothrix brasiliensis is an emerging mycosis in Latin America. One of the problems to quickly treat infected animals and break the transmission chain is associated with the time-consuming gold-standard diagnosis method (culture). We aimed to evaluate a species-specific polymerase chain reaction (PCR) for the diagnosis of sporotrichosis caused by S. brasiliensis using non-invasive samples. We performed a retrospective cross-sectional study using samples collected with swabs from humans and cats with clinical suspicion of sporotrichosis. Deoxyribonucleic acid (DNA) was extracted using a commercial kit, and a species-specific PCR for S. brasiliensis detection was performed. One hundred ten samples were included. PCR showed a good concordance with culture (86% of agreement) for human and cat samples (Kappa coefficient = 0.722, and 0.727, respectively). In conclusion, our data shows that this adapted PCR using non-invasive samples can be applied to sporotrichosis diagnosis, being a good alternative mainly in regions with a lack of mycologists to identify the fungus in culture, contributing to the control of this emergent zoonosis.

We aimed to evaluate a molecular method for diagnosing sporotrichosis caused by Sporothrix brasiliensis in humans and cats. We observed that the technique is in good agreement with the classic method and is a good alternative for assisting in the diagnosis and consequent control of this zoonosis.

A Cluster of Diutina catenulata Funguria in Patients with Coronavirus Disease 2019 (COVID-19) Hospitalized in a Tertiary Reference Hospital from Rio de Janeiro, Brazil.

During the COVID-19 pandemic, fungal infections, especially pulmonary aspergillosis, mucormycosis, and invasive candidiasis, have emerged as a significant health concern. Beyond Candida albicans, the most common cause of invasive candidiasis, other rare ascomycetous yeast species have been described in tertiary care units, potentially posing a broader health threat. We have isolated, from September 2020 to June 2021, nine Diutina catenulata strains from urine samples of six patients. This was intriguing as this fungus had not been previously identified in our institution, nor after June 2021. Therefore, we decided to outline the clinical features of the patients with this rare pathogen, to describe phenotypic characteristics, including antifungal susceptibility profiles, of this yeast species and to identify the genetic makeup through whole-genome sequencing analysis to evaluate if this was a cluster of genetically similar D. catenulata isolates in our institution. The strains were identified through MALDI-TOF MS analyses and Sanger sequencing of two rDNA regions. All patients yielding D. catenulata from urine samples needed ventilator support and used urinary catheters during hospitalization for treatment of COVID-19. None of them had received COVID-19 vaccines. Morphological and biochemical profiles of the nine strains were largely consistent, although fluconazole susceptibility varied, ranging from 4 to 32 µg/mL. Phylogenomic analysis revealed minimal genetic variation among the isolates, with low intrapopulation variation, supported by the identification of only 84 SNPs across all strains. Therefore, we propose that the yeast strains isolated were part of a cluster of D. catenulata funguria in the context of COVID-19.

Antibody Isotype and Subclass Responses in Human Patients With Different Clinical Presentations of Sporotrichosis.

Sporotrichosis diagnosis involves a series of analyses, including culture and antibody detection in serum samples. Serologic methods may sometimes yield false-negative or false-positive results, leading to inaccurate diagnoses. This study assessed specific patient groups in which antibody detection of different isotypes and subclasses may lack sensitivity. An enzyme-linked immunosorbent assay (ELISA) with Sporothrix brasiliensis exoantigens was used to investigate IgM, IgG, IgG1, IgG2, IgG3, IgG4, IgA, IgA1 and IgA2 antibodies in human serum samples. Eighty serum samples from patients with different sporotrichosis clinical manifestations, including cutaneous forms with and without hypersensitivity manifestations, extracutaneous forms (bone, ocular, meningeal and pulmonary), disseminated cutaneous forms and disseminated forms in individuals living with HIV/AIDS, diabetics and alcoholics, were evaluated. The ELISA sensitivities in the detection of different antibodies ranged from 0.85 to 0.60 for the detection of IgG2 and IgG3, respectively. The antibodies with higher area under ROC curves were IgG2, IgG, IgA and IgA1. There were no significant differences in the immunological reactivity of the tested antibodies among different clinical forms of sporotrichosis. The data revealed a higher likelihood of a false-negative outcome in patients with lesions in the nasal mucosa regarding the detection of IgM and a lower likelihood in patients with lymphocutaneous sporotrichosis regarding the detection of IgG3. Patients with hypersensitivity manifestations had a 3.71 odds ratio to yield negative results in total IgG detection. In conclusion, we identified specific patient groups in which antibody detection may lack sensitivity, thus contributing to a better understanding of the diagnostic challenges associated with this condition.

The present and future research agenda of sporotrichosis on the silver anniversary of zoonotic sporotrichosis in Rio de Janeiro, Brazil.

Twenty-five years have passed since the initial observation of endemic zoonotic sporotrichosis in Rio de Janeiro, Brazil. Since then, this disease has spread throughout South America. Accompanying the emergence of this mycosis, some progress has been made, including the expansion of a research network in this field and higher visibility of sporotrichosis within government authorities and funding agencies. However, there are still some challenges to curbing the expansion of this disease in the coming years. These include the development of rapid and accurate diagnostic tests, new antifungal drugs, particularly for the treatment of extracutaneous manifestations of sporotrichosis, and more comprehensive care for cats with sporotrichosis. Including these actions in the sporotrichosis research agenda is required so as to change the development of this disease in the years to come.

Loop-Mediated Isothermal Amplification for the Diagnosis of Sporotrichosis by Sporothrix brasiliensis.

We aimed to develop and validate a Loop-mediated Isothermal Amplification (LAMP) assay to Sporothrix brasiliensis. LAMP reaction was developed using six primers designed based on calmodulin gene. In the LAMP reaction, we tested twenty isolates of S. brasiliensis from animals and humans, along with ten tissue samples extracted from the left footpad of mice that had been experimentally infected with S. brasiliensis. In addition, it included DNA samples from various other fungal species for specificity evaluation. All S. brasiliensis isolates yielded positive results in the LAMP, and the limit of DNA detection was 1 ng/µL. All murine samples were positive in the test while DNA from other fungal species were all negative, resulting in 100% of sensitivity and specificity of primers. LAMP diagnosis technique is a promising alternative to sporotrichosis diagnosis, in a simple and cost-effective way. Further studies are warranted to validate this technique using animal model samples obtained from both humans and animals.

Development and validation of a new quantitative reverse transcription PCR assay for the diagnosis of human sporotrichosis.

Sporotrichosis is an emergent public health problem. The mycological diagnosis of this infection is based on culture, which is fastidious and may represent a biohazard for technicians. Although not widely implemented in routine diagnosis, molecular methodologies are fast, have good accuracy, and can be easily standardized, aiding in the early diagnosis of neglected mycoses. This study aimed at implementing a new pan-Sporothrix quantitative reverse transcription PCR (RT-qPCR) assay, and then validating it on clinical samples from confirmed human sporotrichosis cases. A total of 68 human samples with culture-confirmed diagnosis of sporotrichosis were collected from 64 patients followed at a Brazilian reference center for endemic mycoses. These samples were submitted to whole nucleic acid extraction, followed by an RT-qPCR protocol. The limit of detection was 244 fg, the efficiency was 2.0 (100%), and the assay could amplify the genetic material of the three major clinically relevant species of the genus Sporothrix. Among the 68 samples analyzed, 62 were positive in RT-qPCR, showing an overall sensitivity of 91.18%, which variated according to the type of biological sample: 96.72% in skin samples (n = 61) and 100% in respiratory samples (n = 3), whereas all cerebrospinal fluid specimens (n = 4) were negative. The specificity was 100% when tested in 25 samples from patients with other mycoses and tuberculosis. In addition, DNA from 93 fungal species did not yield positive results, confirming the high specificity of this test. Our RT-qPCR presented high sensitivity and specificity, representing an excellent tool for a fast and reliable diagnosis of human sporotrichosis.

Sporotrichosis is a deep mycosis with limited laboratorial techniques for fast diagnosis. We developed an assay able to detect the genetic material of fungal agents of sporotrichosis, and validated it in human specimens from patients with this disease, obtaining high positivity and specificity.

Metabolic and phenotypic plasticity may contribute for the higher virulence of Trichosporon asahii over other Trichosporonaceae members.

BACKGROUND: The Trichosporonaceae family comprises a large number of basidiomycetes widely distributed in nature. Some of its members, especially Trichosporon asahii, have the ability to cause human infections. This ability is related to a series of virulence factors, which include lytic enzymes production, biofilm formation, resistance to oxidising agents, melanin and glucuronoxylomannan in the cell wall, metabolic plasticity and phenotypic switching. The last two are poorly addressed within human pathogenic Trichosporonaceae. OBJECTIVE: These factors were herein studied to contribute with the knowledge of these emerging pathogens and to uncover mechanisms that would explain the higher frequency of T. asahii in human infections. METHODS: We included 79 clinical isolates phenotypically identified as Trichosporon spp. and performed their molecular identification. Lactate and N-acetyl glucosamine were the carbon sources of metabolic plasticity studies. Morphologically altered colonies after subcultures and incubation at 37°C indicated phenotypic switching. RESULTS AND CONCLUSION: The predominant species was T. asahii (n = 65), followed by Trichosporon inkin (n = 4), Apiotrichum montevideense (n = 3), Trichosporon japonicum (n = 2), Trichosporon faecale (n = 2), Cutaneotrichosporon debeurmannianum (n = 1), Trichosporon ovoides (n = 1) and Cutaneotrichosporon arboriforme (n = 1). T. asahii isolates had statistically higher growth on lactate and N-acetylglucosamine and on glucose during the first 72 h of culture. T. asahii, T. inkin and T. japonicum isolates were able to perform phenotypic switching. These results expand the virulence knowledge of Trichosporonaceae members and point for a role for metabolic plasticity and phenotypic switching on the trichosporonosis pathogenesis.

Sporotrichosis After Tattooing Caused by Sporothrix brasiliensis.

Sporotrichosis is a subcutaneous mycosis caused by pathogenic species of the genus Sporothrix. Since 1998, the number of cases of sporotrichosis due to Sporothrix brasiliensis has grown significantly in Rio de Janeiro, Brazil. Nearly all cases are related to cats as the main source of fungal infection. We report two cases of sporotrichosis following tattoos, a transmission form of S. brasiliensis not yet reported. The first patient, a 22-year-old female, had cutaneous sporotrichosis, fixed form, over a tattoo in her lumbar region. The lesion appeared 12 weeks after she was tattooed. The second patient, a 27-year-old female, had a lymphocutaneous sporotrichosis over a forearm tattoo. The lesion appeared two weeks after she was tattooed. In both cases there was no history of contact with cats or other plausible source of infection. The present study highlights that other non-zoonotic forms of transmission of S. brasiliensis may occur in endemic areas.

Anti-Sporothrix Antibody Detection in Domestic Cats as an Indicator of a Possible New Occurrence Area for Sporotrichosis in North Brazil.

Feline sporotrichosis has emerged as an important public health issue in some countries, especially Brazil. Currently, zoonotic transmission of Sporothrix brasiliensis by domestic cats is the major sporotrichosis spread form throughout this country. Sporotrichosis in Brazil is a good model for the One Health concept application, which connects the environment, human and animal health. Under this thinking, the aim of this study was to investigate the seroprevalence of sporotrichosis in cats from Rolim de Moura, Rondônia, Brazil, using antibody detection by an ELISA test previously validated for human diagnosis. For the standardization of this test, 30 serum samples from cats with proven sporotrichosis and 11 sera from healthy cats were used. The assay showed 87% sensitivity and 100% specificity for the diagnosis of feline sporotrichosis. After the standardization, 202 serum samples from distinct cats from Rolim de Moura were evaluated. The test was positive in 63 (31.19%) cats from the studied area. A multivariate analysis revealed that living far from forest or agricultural areas as well as pure breed animals had higher odds ratios (3.157 and 2.281, respectively) for the presence of detectable levels of anti-Sporothrix antibodies. These results show the applicability of this assay in the detection of anti-Sporothrix antibodies in feline serum samples and point to a putative new occurrence area of urban sporotrichosis dispersing to the North region of Brazil.

Zoonotic sporotrichosis in renal transplant recipients from Rio de Janeiro, Brazil.

Sporotrichosis is the main subcutaneous mycosis in the world. In the last two decades, zoonotic sporotrichosis transmitted by cats has become hyperendemic in Rio de Janeiro, Brazil. Renal transplant recipients are subject to invasive fungal infection because of the effects of immunosuppressive therapy, but sporotrichosis is rarely reported. The authors conducted a retrospective study describing epidemiological, clinical, and therapeutic data related to adult renal-transplant-recipient patients diagnosed with sporotrichosis. The molecular identification of fungal isolates was performed. Minimal inhibitory concentration (MIC) of amphotericin B (AMB), itraconazole (ITZ), posaconazole (POS), isavuconazole, and terbinafine (TRB) against the strains was determined using the protocol described by the Clinical and Laboratory Standards Institute (CLSI). Six cases were identified from a cohort with 2429 sporotrichosis patients. They were five men and one woman, with a mean age of 44.2 years (range: 34-54 years). Four of them had cutaneous limited forms, and two patients had disseminated forms. The mean time between transplant and the onset of sporotrichosis symptoms was 25.5 (range: 6-36) months. Sporothrix brasiliensis was identified as the causative agent. The isolates were classified as wild type for all antifungal drugs tested. Treatment schemes included AMB (deoxycholate and liposomal), ITZ, and TRB. Five patients evolved to cure, and one died as a result of disseminated disease. Renal transplant recipients may be a vulnerable group for sporotrichosis in endemic countries. The authors highlight the importance of sporotrichosis prevention, early diagnosis, and treatment to prevent disseminated disease and poor prognosis.

Production of Secreted Carbohydrates that Present Immunologic Similarities with the Cryptococcus Glucuronoxylomannan by Members of the Trichosporonaceae Family: A Comparative Study Among Species of Clinical Interest.

Glucuronoxylomannan (GXM) participates in several immunoregulatory mechanisms, which makes it an important Cryptococcus virulence factor that is essential for the disease. Trichosporon asahii and Trichosporon mucoides share with Cryptococcus species the ability to produce GXM. To check whether other opportunistic species in the Trichosporonaceae family produce GXM-like polysaccharides, extracts from 28 strains were produced from solid cultures and their carbohydrate content evaluated by the sulfuric acid / phenol method. Moreover, extracts were assessed for cryptococcal GXM cross-reactivity through latex agglutination and lateral flow assay methods. Cryptococcus neoformans and Saccharomyces cerevisiae were used as positive and negative controls, respectively. In addition to T. asahii, the species Trichosporon inkin, Apiotrichum montevideense, Trichosporon japonicum, Trichosporon faecale, Trichosporon ovoides, Cutaneotrichosporon debeurmannianum, and Cutaneotrichosporon arboriformis are also producers of a polysaccharide immunologically similar to the GXM produced by human pathogenic Cryptococcus species. The carbohydrate concentration of the extracts presented a positive correlation with the GXM contents determined by titration of both methodologies. These results add several species to the list of fungal pathogens that produce glycans of the GXM type and bring information about the origin of potential false-positive results on immunological tests for diagnosis of cryptococcosis based on GXM detection.

Paracoccidioides brasiliensis habitat: far beyond armadillo burrows?

Paracoccidioides spp. isolation from environmental samples is rare and hardly reproducible. Molecular techniques have facilitated the fungal detection. However, it can be still difficult. Some strategies to enhance the capacity of DNA detection have been adopted, including the analysis of soil samples belonging to the habitat of animals from which Paracoccidioides spp. have already been isolated, notably armadillo burrows. To date, the detection of Paracoccidioides spp. has not yet been reported from outbreak hotspots. Clusters and outbreaks of acute paracoccidioidomycosis (PCM), usually a more severe clinical form, have currently occurred in urban areas being associated to climate changes, deforestation, and great constructions. These occurrences potentially signalise the fungus' environmental niche, a riddle not yet solved. The authors performed an environmental investigation in a deeply disturbed area, after a highway construction in Rio de Janeiro, Brazil, where a recent outbreak of acute PCM occurred. Specific DNA sequences of Paracoccidioides brasiliensis were detected in shallow soil samples around the highway, reinforcing the association between the road construction and this PCM outbreak.

Comparative Analysis of Putative Virulence-Associated Factors of Microsporum canis Isolates from Human and Animal Patients.

Microsporum canis is a zoophilic dermatophyte and the most common fungus isolated from dogs and cats worldwide. To invade skin, this pathogen uses different enzymes, which may be associated with virulence, that contribute to the fungal pathogenicity. The aim of this study is to compare the expression of enzymes that may be associated with virulence, and thermotolerance of M. canis strains isolated from dogs, cats, and humans. The in vitro expression of the enzymes keratinase, catalase, urease, hemolysin, and aspartic protease was evaluated in 52 M. canis strains recently isolated from 14 human patients, 12 dogs, 15 symptomatic, and 11 asymptomatic cats. In addition, thermotolerance was assessed by comparative analysis of fungal growth at 25 °C and 35 °C. Keratinase activity was low in 34 and moderate in 18 strains. Aspartic-protease activity was low in 7, moderate in 33, and high in 12 strains. Hemolysin activity was low in 44 and moderate in 8 strains. All strains were classified as low producers of catalase. All but three strains produced urease in vitro, with a broad range of activity. The strains presented in vitro growth at the two studied temperatures were classified as presenting low (36.5%), medium (44.3%), or high (19.2%) thermotolerance. There was no statistically significant difference in the new putative virulence-associated factors studied among the different hosts, which suggests that they may have a similar role on human, cat, and dog infection. Also, no difference was observed between strains isolated from symptomatic and asymptomatic cats. This suggests that these factors have a limited impact on the fate of feline dermatophytosis caused by M. canis.

Role of western blot assay for the diagnosis of histoplasmosis in AIDS patients from a National Institute of Infectious Diseases in Rio de Janeiro, Brazil.

BACKGROUND: Histoplasmosis is a frequent fungal infection in HIV/AIDS patients, with high morbimortality rates when diagnosis and treatment are delayed. Antibody detection, which is faster than the gold standard culture test, hastens the laboratory investigation. OBJECTIVES: To evaluate the role of WB for antibody detection in the diagnosis of histoplasmosis among HIV/AIDS patients. PATIENTS AND METHODS: Fifty patients with proven or probable histoplasmosis were included. Clinical, epidemiological and laboratory data were described in the same population after a review of their medical records. WB was performed using deglycosylated histoplasmin. RESULTS: About 82% of patients were adult males and the mean age was 39.3 years. CD4+ T lymphocyte count less than 150 cells/mm3 was observed in 62% patients. Antibodies against Histoplasma capsulatum M antigen were detected in 62% of patients, and against both M and H antigens in 28% of individuals. Sera from 10% of patients were nonreactive. Histoplasmosis was the first opportunistic infection in 38% of the cases. Disseminated and pulmonary histoplasmosis occurred in 84% and 16% of patients, respectively. The overall mortality was 16%. CONCLUSION: WB could be useful for the histoplasmosis diagnosis in HIV/AIDS patients because of its easefulness and good sensitivity in a population where antibody production is hampered.

A case of sporotrichosis caused by different Sporothrix brasiliensis strains: mycological, molecular, and virulence analyses.

BACKGROUND: Sporotrichosis is a subcutaneous mycosis caused by dimorphic pathogenic fungi belonging to the Sporothrix genus. Pathogenic Sporothrix species typically produce melanin, which is known to be a virulence factor. OBJECTIVES: The aim of this study was to perform phenotypic, genotypic, and virulence analyses of two distinct Sporothrix brasiliensis strains isolated from the same lesion on a patient from Rio de Janeiro. METHODS AND FINDINGS: Genotypic analyses by partial sequencing of the calmodulin, ß-tubulin, and chitin synthase genes, as well as polymerase chain reaction (PCR)-fingerprinting by T3B, M13, and GACA, showed that the isolates were very similar but not identical. Both isolates had similar phenotypic characteristics and effectively produced melanin in their yeast forms, accounting for their ability of causing disease in a murine sporotrichosis model. Remarkably, isolate B was albino in its environmental form but caused more severe disease than the pigmented A isolate. CONCLUSIONS: These findings indicate that the patient was infected by two genetically and biologically distinct S. brasiliensis that vary in their production of melanin in their environmental forms. The results underscore the importance of characterizing phenotypically different isolates found in the same clinical specimen or patient.

Interaction with Pantoea agglomerans Modulates Growth and Melanization of Sporothrix brasiliensis and Sporothrix schenckii.

Sporothrix brasiliensis and Sporothrix schenckii stand as the most virulent agents of sporotrichosis, a worldwide-distributed subcutaneous mycosis. The origin of Sporothrix virulence seems to be associated with fungal interactions with organisms living in the same environment. To assess this hypothesis, the growth of these two species in association with Pantoea agglomerans, a bacterium with a habitat similar to Sporothrix spp., was evaluated. Growth, melanization, and gene expression of the fungus were compared in the presence or absence of the bacterium in the same culture medium. Both S. brasiliensis and S. schenckii grew in contact with P. agglomerans yielding heavily melanized conidia after 5 days of incubation at 30 °C in Sabouraud agar. This increased melanin production occurred around bacterial colonies, suggesting that fungal melanization is triggered by a diffusible bacterial product, which is also supported by a similar pattern of melanin production during Sporothrix spp. growth in contact with heat-killed P. agglomerans. Growth of P. agglomerans was similar in the presence or absence of the fungus. However, the growth of S. brasiliensis and S. schenckii was initially inhibited, but further enhanced when these species were co-cultured with P. agglomerans. Moreover, fungi were able to use killed bacteria as both carbon and nitrogen sources for growth. Representational difference analysis identified overexpressed genes related to membrane transport when S. brasiliensis was co-cultured with the bacteria. The down-regulation of metabolism-related genes appears to be related to nutrient availability during bacterial exploitation. These findings can lead to a better knowledge on Sporothrix ecology and virulence.

High variability within Candida albicans transcription factor RLM1: Isolates from vulvovaginal infections show a clear bias toward high molecular weight alleles.

Previous studies have correlated the severity of recurrent vulvovaginal Candida infections (VVC) and balanitis in patients from China with the presence of some dominant genotypes at the ORF RLM1. Here we tested VVC vs non-VVC isolates from Portugal, Brazil and Greece and, although the same genotypes were identified in VVC isolates, they were present in only five out of 150 strains. However, this analysis showed that VVC isolates presented a higher percentage of genotypes with similar high molecular weight alleles, in comparison with strains isolated from other biological sources.

L-tyrosine induces the production of a pyomelanin-like pigment by the parasitic yeast-form of Histoplasma capsulatum.

Melanization of Histoplasma capsulatum remains poorly described, particularly in regards to the forms of melanin produced. In the present study, 30 clinical and environmental H. capsulatum strains were grown in culture media with or without L-tyrosine under conditions that produced either mycelial or yeast forms. Mycelial cultures were not melanized under the studied conditions. However, all strains cultivated under yeast conditions produced a brownish to black soluble pigment compatible with pyomelanin when grew in presence of L-tyrosine. Sulcotrione inhibited pigment production in yeast cultures, strengthening the hyphothesis that H. capsulatum yeast forms produce pyomelanin. Since pyomelanin is produced by the fungal parasitic form, this pigment may be involved in H. capsulatum virulence.

Evaluation of melanin production by Sporothrix luriei.

There is a paucity of studies on the cell biology of Sporothrix luriei, the less common of the pathogenic Sporothrix species worldwide. The production of DHN-melanin, eumelanin, and pyomelanin were evaluated on the mycelial and yeast forms of the S. luriei ATCC 18616 strain. The mycelial form of this species produced only pyomelanin, which protected the fungus against environmental stressors such as ultraviolet light, heat, and cold. The yeast form was unable to produce any of the tested melanin types. The lack of melanin in the parasitic form of S. luriei may be an explanation for its low frequency in human infections.