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Background: Paracoccidioidomycosis (PCM) is Latin America's most prevalent systemic mycosis, carrying an important social burden. Its agent, Paracoccidioides brasiliensis, has rarely been identified in nature. Studies characterizing acute/subacute PCM incidence and their relationship with climate variables are not available. This work analysed a series of acute/subacute cases that occurred in the Botucatu area, São Paulo State, Brazil, from 1969 to 1999, as an outcome of weather variability., Methods: Stepwise regression of annual data was applied to model incidence, calculated based on 91 cases, from lagged variables: antecedent precipitation, air temperature, soil water storage, absolute and relative air humidity, and Southern Oscillation Index (SOI)., Results: Multiple regression analyses resulted in a model, which explains 49% of the incidence variance, taking into account the absolute air humidity in the year of exposure, soil water storage and SOI of the previous 2 years., Conclusions: The correlations may reflect enhanced fungal growth after increase in soil water storage in the longer term and greater spore release with increase in absolute air humidity in the short term.

Pythium insidiosum causes pythiosis, a life-threatening disease that occurs in tropical regions and affects man and animals. Although pythiosis in Brazil had been described in various animal species, the first human case was only recently reported. The present study aimed to characterize the morphologic and molecular characteristics of a new equine isolate of P. insidiosum and compare them with those of the first Brazilian human isolate. Both isolates were recovered from the same region of the country. Macroscopic and microscopic features were evaluated in two culture media. Sporangia formation and zoospore release were obtained after culturing the isolates with fragments of grasses and crops in an appropriate liquid induction medium. The molecular analysis of the isolates consisted of the complete sequencing of the ITS-5.8S rDNA region and sequences of both showed identical composition of 836 bp and 99% similarity with the isolates M16, 65, M12, 339 and 394 deposited at GenBank. Simple mycological procedures such as the production of sporangia and zoospores may distinguish P. insidiosum from zygomycetes. The rDNA sequencing indicates that, in Brazil, both humans and animals might be infected by a common genotype of the pathogen.

The mycelia-to-yeast (M-Y) transition, thermal tolerance and virulence profiles were evaluated for nine isolates of Paracoccidioides brasiliensis, including samples from two of the three recently discovered cryptic species, as well as their relation to the partial sequence and transcription of the hsp70 gene. The isolates Bt84 and T10 (from PS2 species) took more time to convert to yeast form and presented elongated yeast cells at 36 degrees C. Arthroconidia production was also observed during the M-Y transition for some isolates. Our data confirm that the hsp70 transcription may be associated with thermal tolerance, but this does not seem to be directly related to high virulence profiles. The partial sequencing of this gene allowed the separation of our isolates into two clusters that correspond to the two sympatric cryptic species occurring in an area hyperendemic for PCM (Botucatu, SP, Brazil).

The knowledge on the biological aspects of Paracoccidioides brasiliensis has evolved greatly since the first description of the disease in 1908. From the pioneers, who were able to clearly demonstrate the fungal nature of the agent, to the recent genomic era, important advances have been achieved. P. brasiliensis is a true fungus, belonging to the Ascomycetous Division, although its sexual phase has not been demonstrated morphologically. A better understanding of the fundamental aspects of the agent, especially its phylogeny and evolutionary history, will provide us with valuable insights allowing a better comprehension of the disease and our capacity to deal with the problem. Concerning the fungus's ecology, although some progress had been observed, the ecological niche of the pathogen has not been determined yet. The aim of the present review is to focus on the biological aspects of P. brasiliensis from an evolutionary point of view, addressing the fungus's phylogenetic aspects, in those special points that might be relevant for the pathogen/host interactions, the biological forces that have been acting on its origin and maintenance of virulence, as well as in determining the fungus's ecology and epidemiology.

Paracoccidioides brasiliensis causes paracoccidioidomycosis (PCM) that is one of the most prevalent systemic human mycoses in Latin America. Armadillos show a high incidence of PCM infection and could, therefore, be a natural reservoir for this fungus. In this study were compared the virulence profiles of isolates obtained from nine-banded armadillos (Dasypus novemcinctus) (PbT1 and PbT4) and isolates from PCM patients (Pb265 and Bt83). Pathogenicity was evaluated by fungal load and analysis of colony morphology. Immunity against the fungus was tested by delayed type hypersensitivity test (DTH) and antibody quantification by ELISA. The higher virulence of PbT1 and PbT4 was suggested by higher fungal load in spleen and lungs. Armadillo isolates and Bt83 presented a cotton-like surface contrasting with the cerebriform appearance of Pb265. All isolates induced cellular and humoral immune responses in infected BALB/c mice. DTH reactions were similarly induced by the four isolates, however, a great variability was observed in specific antibody levels, being the highest ones induced by Bt83 and PbT4. The present work confirms that armadillos harbor P. brasiliensis, whose multiplication and induced immunity in experimentally infected mice are heterogeneous, resembling the behavior of isolates from human PCM. This study reinforces the possibility that armadillos play an important role in the biological cycle of this pathogen.

Paracoccidioides brasiliensis is the etiologic agent of paracoccidioidomycosis, a disease confined to Latin America and of marked importance in the endemic areas due to its frequency and severity. This species is considered to be clonal according to mycological criteria and has been shown to vary in virulence. To characterize natural genetic variation and reproductive mode in this fungus, we analyzed P. brasiliensis phylogenetically in search of cryptic species and possible recombination using concordance and nondiscordance of gene genealogies with respect to phylogenies of eight regions in five nuclear loci. Our data indicate that this fungus consists of at least three distinct, previously unrecognized species: S1 (species 1 with 38 isolates), PS2 (phylogenetic species 2 with six isolates), and PS3 (phylogenetic species 3 with 21 isolates). Genealogies of four of the regions studied strongly supported the PS2 clade, composed of five Brazilian and one Venezuelan isolate. The second clade, PS3, composed solely of 21 Colombian isolates, was strongly supported by the alpha-tubulin genealogy. The remaining 38 individuals formed S1. Two of the three lineages of P. brasiliensis, S1 and PS2, are sympatric across their range, suggesting barriers to gene flow other than geographic isolation. Our study provides the first evidence for possible sexual reproduction in P. brasiliensis S1, but does not rule it out in the other two species.

Pythiosis, caused by Pythium insidiosum, occurs in humans and animals and is acquired from aquatic environments that harbor the emerging pathogen. Diagnosis is difficult because clinical and histopathologic features are not pathognomonic. We report the first human case of pythiosis from Brazil, diagnosed by using culture and rDNA sequencing.