Effect Of Voriconazole On Azole Resistant Gene Expression In Aspergillus Fumigatus Associated With Fungal Keratitis.

To study the effect of voriconazole on selected azole resistance gene expression in Aspergillus fumigatus associated fungal keratitis.

Tertiary eye care center of eastern India

Culture positive Aspergillus keratitis was selected for this study. Antifungal susceptibility and MICs were recorded against voriconazole. Three selective doses of below MICs (1mg, 0.5mg, 0.25mg and 0.12mg) were applied to Aspergillus fumigatus and subcultured. In every subculture, selective azole resistance gene expression (Cyp51, L98H, T289A, Y121F) was studied. After the 8^th generation, the same fungal species was subcultured again without adding any azoles to the culture. In every batch, gene expression was measured.

Initially, in vivo, no azole resistance was found with the selective fungi. From the 7^th generation, all suboptimal doses of voriconazole showed the expression of azole resistance genes (Ct value range 18-32 in qPCR). This gene expression came back to normal pattern from 5^th generation at higher doses when azole exposure stopped, but low grade azole resistance gene expressions were still found at lower suboptimal doses (0.25mg & 0.12mg) where no azole was added invitro upto 7^th generation (Ct value range 28-30 in qPCR). An irreversible azole resistance gene expression was noted. 

Continuous exposure to suboptimal doses of azole can give rise the azole resistance. In communities, azole resistance among Aspergillus is uncommon. Before giving azole in fungal keratitis as treatment. Screening of azole resistance is an important approach to initiating antifungal medications. Further gene expression should be checked to findout the endpoint of the expression.