Background: Sporotrichosis is a chronic subcutaneous mycosis of humans and animals, which is typically acquired by traumatic
inoculation of plant material contaminated with Sporothrix propagules, or via animals, mainly felines. Sporothrix infections
notably occur in outbreaks, with large epidemics currently taking place in southeastern Brazil and northeastern China. Pathogenic
species include Sporothrix brasiliensis, Sporothrix schenckii s. str., Sporothrix globosa, and Sporothrix luriei, which exhibit
differing geographical distribution, virulence, and resistance to antifungals. The phylogenetically remote species Sporothrix
mexicana also shows a mild pathogenic potential.
Methods: We assessed a genetically diverse panel of 68 strains.
Susceptibility profiles of medically important Sporothrix species were evaluated by measuring the MICs and MFCs for amphotericin
B (AMB), fluconazole (FLC), itraconazole (ITC), voriconazole (VRC), posaconazole (PCZ), flucytosine (5FC), and caspofungin
(CAS). Haplotype networks were constructed to reveal interspecific divergences within clinical Sporothrix species to evaluate
genetically deviant isolates.
Results: ITC and PCZ were moderately effective against S. brasiliensis (MIC90 = 2 and
2 μg/mL, respectively) and S. schenckii (MIC90 = 4 and 2 μg/mL, respectively). PCZ also showed low MICs against the rare species
S. mexicana. 5FC, CAS, and FLC showed no antifungal activity against any Sporothrix species. The minimum fungicidal concentration
ranged from 2 to >16 μg/mL for AMB against S. brasiliensis and S. schenckii, while the MFC90 was >16 μg/mL for ITC,
VRC, and PCZ.
Conclusion: Sporothrix species in general showed high degrees of resistance against antifungals. Evaluating
a genetically diverse panel of strains revealed evidence of multidrug resistant phenotypes, underlining the need for molecular
identification of etiologic agents to predict therapeutic outcome.