Impact of TR34/L98H, TR46/Y121F/T289A and TR53 Alterations in Azole-Resistant Aspergillus fumigatus on Sterol Composition and Modifications after In Vitro Exposure to Itraconazole and Voriconazole. Microorganisms.
Alvarez-Moreno C. 04/01/2022
Background: Sterols are the main components of fungal membranes. Inhibiting their biosynthesis is the mode of action of azole antifungal drugs that are widely used to treat fungal disease including aspergillosis. Azole resistance has emerged as a matter of concern but little is known about sterols biosynthesis in azole resistant Aspergillus fumigatus. Methods: We explored the sterol composition of 12 A. fumigatus isolates, including nine azole resistant isolates with TR34/L98H, TR46/Y121F/T289A or TR53 alterations in the cyp51A gene and its promoter conferring azole resistance. Modifications in sterol composition were also investigated after exposure to two azole drugs, itraconazole and voriconazole. Results: Overall, under basal conditions, sterol compositions were qualitatively equivalent, whatever the alterations in the target of azole drugs with ergosterol as the main sterol detected. Azole exposure reduced ergosterol composition and the qualitative composition of sterols was similar in both susceptible and resistant isolates. Interestingly TR53 strains behaved differently than other strains.
Conclusions: Elucidating sterol composition in azole-susceptible and resistant isolates is of interest for a better understanding of the mechanism of action of these drugs and the mechanism of resistance of fungi. Conclusions In this study, we described for the first-time relative sterol composition of azole-resistant Aspergillus isolates with complex alterations in the cyp51A gene and/or its promotor, which are linked to environmental exposition to azole fungicides. This study highlights that TR34/L98H and TR46/Y121F/T289A alterations had no impact on relative composition of sterols in basal conditions when compared with susceptible isolates. Moreover, in our conditions, after itraconazole and voriconazole exposure the qualitative composition of sterols was similar in susceptible and resistant isolates. Interestingly in basal condition relative ergosterol content was higher for TR53 strains and it was significantly lower than for other alterations after itraconazole and voriconazole treatment. It would be interesting to look for other mechanisms of resistance in these isolates. Moreover, in this study we did not explore point substitution in 14α-lanosterol demethylase (including M220 and G54); it could be of interest to compare the effects of point mutation with the effects of complex alterations studied here.