Virulence assessment of Sporothrix species from clinical and environmental clades using Tenebrio molitor as an experimental model.

Sporotrichosis is a neglected subcutaneous mycosis of global distribution caused by thermally dimorphic Sporothrix species. Despite their pathogenic potential in vertebrates, the virulence mechanisms underlying their interactions with other organisms remain poorly understood. This study employed the coleopteran insect Tenebrio molitor as an experimental model to evaluate the virulence of seven Sporothrix species from clinical (S. brasiliensis, S. schenckii, S. globosa, S. luriei) and environmental (S. pallida, S. mexicana, S. chilensis) clades. Larvae were inoculated with conidia or yeast cells and assessed for survival, fungal burden (colony-forming units), histopathology, hemocyte count, and antimicrobial peptide (AMP) gene expression. Virulence patterns in this model paralleled those observed in mammalian hosts, with S. schenckii and S. brasiliensis showing higher virulence (30-40% larval survival). Distinct profiles were observed between fungal phases, the yeast phase generally showing increased virulence. Interestingly, contrary to murine models, environmental species S. pallida and S. chilensis exhibited unexpectedly high virulence in the mycelial phase (larval survival of 30% and 10%, respectively). Additionally, AMP genes (Thaumatin-like 1 and Tenecin 3) were more strongly expressed in larvae infected with S. brasiliensis and S. pallida. These findings suggest that the T. molitor immune response to Sporothrix may be influenced by the evolutionary history of both the host and the fungal genus. Overall, our results highlight the intricate relationship between fungal virulence, host immunity, and ecological factors shaping the outcome of Sporothrix infections in T. molitor.