OXIDATIVE STRESS RESPONSE IN ENVIRONMENTAL AND PATHOGENIC SPOROTHRIX SPECIES

The fungal genus Sporothrix comprises a group of thermodimorphic pathogens that cause sporotrichosis, a (sub)cutaneous infection of humans and felines. The disease is worldwide distributed and results from two major infection routes: animal transmission and plant origin. S. schenckii is the classical pathogen of the group. The infectious species compose a “pathogenic clade” in the genus Sporothrix, with S. brasiliensis, S. globosa and S. luriei as members. However, the genus also contains occasional opportunists, such as S. pallida and S. mexicana, which have a much lower potential to cause infection in mammals. In this study we performed phenotypic tests to investigate on the oxidative stress response among pathogenic and non-pathogenic Sporothrix species. A total of 68 strains, isolated from humans, from cats and from the environment were examined. The identity of all strains was verified using partial sequencing of the calmodulin-encoding gene. Subsequently they were inoculated in yeast extract peptone dextrose agar with and without H2O2 (6 mM). The results revealed that the non-pathogenic strains (S. pallida and S. mexicana) were able to grow in the presence of H2O2, whereas pathogenic species showed different responses to oxidative stress. All S. schenckii strains were unable to grow in YEPD + H2O2 whereas 58.8% of S. brasiliensis and 66.6% of S. globosa strains grew well under these conditions. Overall our data showed that Sporothrix species respond in a different manner to oxidative stress and suggest further studies, especially to molecular level, to decipher the gene regulatory network involved in this phenomenon.