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

Abstract

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.

Keywords: Cryptococcus neoformans; propiconazole; resistance; soil; triazole.

Fig 1

Dissipation curves of propiconazole in the soil.

Fig 2

The MICs of clinical triazoles (FLU, fluconazole; VOR, voriconazole; ITR, itraconazole; POS, posaconazole) against the resistant strains of C. neoformans isolated from propiconazole-contaminated soil.

Fig 3

MICs of three resistant C. neoformans before and after 15 consecutive transfers to four medical triazoles (FLU, fluconazole; VOR, voriconazole; ITR, itraconazole; POS, posaconazole).

Fig 4

Relative expression levels of ERG11, AFR1, AFR2, AFR3, and MDR1 of the three resistant strains with stable resistance inheritance. Expression levels of ERG11 and these efflux pump genes were evaluated in comparison with the expression of these same genes in the original strain P1, in the absence of the pesticide used to obtain the tested isolates. The letters indicate the difference in expression levels (P < 0.05, Duncan’s test).

Fig 5

The chemical structures of propiconazole, its major competitors, and triazole antifungals.