Abstract
The opportunistic pathogen Aspergillus fumigatus has developed worldwide resistance to azoles largely through mutations in cytochromeP450 enzyme Cyp51. In this study, we indicated that in vitro azole situation results in emergence of azole-resistant mutations. There are previously identified azole-resistant cyp51A 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 Galleria mellonella model of A. fumigatus 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 cyp51A mutations conferring azole resistance in A. fumigatus.
Highlights
Aspergillus fumigatus, the most common Aspergillus species, is a major opportunistic fungal pathogen and may lead to a variety of allergic reactions and life-threatening systemic infections in humans, including invasive pulmonary aspergillosis, pulmonary aspergilloma, and allergic bronchopulmonary aspergillosis (Hagiwara et al, 2016; Chowdhary et al, 2017)
There are previously identified azole-resistant cyp51A 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
This study suggests that drug selection pressure make it possible to isolate unidentified cyp51A mutations conferring azole resistance in A. fumigatus
Summary
Aspergillus fumigatus, the most common Aspergillus species, is a major opportunistic fungal pathogen and may lead to a variety of allergic reactions and life-threatening systemic infections in humans, including invasive pulmonary aspergillosis, pulmonary aspergilloma, and allergic bronchopulmonary aspergillosis (Hagiwara et al, 2016; Chowdhary et al, 2017). Antifungal drugs are limited for treatment options and they include three classes: polyenes (amphotericin B), azoles and echinocandins. Azoles are the preferred agents for first-line prophylaxis and treatment of aspergillosis (Walsh et al, 2008; Garcia-Rubio et al, 2017). The treatment of invasive infections has proved to be difficult because of limited antifungal drugs and occurrence of antifungalresistant strains worldwide and the host immunocompromised status (Shao et al, 2007). It is reported that clinical long-term azole therapy tends to promote the emergence of the azoleresistant strains (Camps et al, 2012; Tashiro et al, 2012; Chowdhary et al, 2017). For the treatment and effective maintenance therapy of chronic aspergillosis, prolonged antifungal therapy is needed (Godet et al, 2016).
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