Uncovering New Mutations Conferring Azole Resistance in the Aspergillus fumigatus cyp51A Gene

Abstract

The opportunistic pathogen <i>Aspergillus fumigatus</i> has developed worldwide resistance to azoles largely through mutations in cytochromeP450 enzyme Cyp51. In this study, we indicated that <i>in vitro</i> azole situation results in emergence of azole-resistant mutations. There are previously identified azole-resistant <i>cyp51A</i> mutations (M220K, M220I, M220R, G54E and G54W mutations) and we successfully identified in this study two new mutations (N248K/V436A, Y433N substitution) conferring azole resistance among 18 independent stable azole-resistant isolates. The <i>Galleria mellonella</i> model of <i>A. fumigatus</i> infection experiment verified that Cyp51A mutations N248K/V436A and Y433N reduce efficacy of azole therapy. In addition, a predicted Cyp51A 3D structural model suggested that Y433N mutation causes the reduced affinities between drug target Cyp51A and azole antifungals. This study suggests that drug selection pressure make it possible to isolate unidentified <i>cyp51A</i> mutations conferring azole resistance in <i>A. fumigatus</i>.