Agricultural propiconazole residues promote triazole cross-resistance in Cryptococcus neoformans through ERG11 and efflux pump overexpression.

Fluconazole remains a cornerstone for consolidation therapy in cryptococcal meningitis. However, resistance poses a significant risk of treatment failure in sub-Saharan Africa, where fluconazole monotherapy is common. Beyond clinical use, triazole fungicides are suspected drivers of resistance pathways. Nevertheless, there is limited evidence linking triazole fungicide use to the emergence of resistant C. neoformans (RCN) in soil. Here, the possibility of evolving triazole resistance in C. neoformans by exposing it to the triazole fungicide propiconazole was explored. The findings suggest that propiconazole can induce the resistance of C. neoformans to triazole drugs in liquid media and soil by upregulating the expression levels of target gene ERG11 and efflux pump genes AFR1, AFR2, and AFR3. Interestingly, there were 2, 5, 4, and 3 RCN strains isolated from propiconazole-treated soils at 1, 2, 5, and 10 mg/kg, respectively, indicating that the emergence of RCN isolates depends on the residual concentrations of propiconazole. These findings suggest that the field application of propiconazole, even at the recommended dosage, can promote the development of triazole resistance in C. neoformans, thereby affecting the efficacy of triazole drugs and hindering the prevention and management of cryptococcosis.