Abstract
Aspergillus fumigatus triazole resistance is an emerging concern for treating chronically infected/colonized patients. This study sought to evaluate the performance of PCR assays to detect Aspergillus fungi together with azole resistance in sputum samples from cystic fibrosis (CF) patients. In total, 119 sputum samples from 87 CF patients were prospectively processed for Aspergillus detection by means of mycological culture and four qPCR assays, 2 in-house methods and two commercial multiplex real-time PCR assays simultaneously detecting Aspergillus and the most relevant cyp51A gene mutations (MycoGENIE® and AsperGenius®). Azole susceptibility of A. fumigatus isolates was assessed using Etest® method and cyp51A gene mutation were characterized by sequencing. The overall rate of Aspergillus detection with the four qPCR assays ranged from 47.9 to 57.1%, contrasting with 42/119 (35.3%) positive cultures with A. fumigatus. The high sensitivity of PCR on sputum could then contribute to more effective grading of Aspergillus disease in CF patients. Five out of 41 isolated strains (12.2%) exhibited azole-resistant MIC patterns, three of which harbored cyp51A mutations and only 1/3 with the sequence TR34/L98H. Combined with culture, PCR assay achieved high sensitivity Aspergillus screening in CF samples. However, cyp51A targeting was only moderately effective for azole resistance monitoring, while Aspergillus resistance remains of great concern.
Highlights
Aspergillus fumigatus is responsible for severe asthma or allergic bronchopulmonary aspergillosis (ABPA) in up to 15% of cystic fibrosis (CF) patients (Stevens et al, 2003; Pihet et al, 2009), though the significance of its detection is often questioned when there are no accompanying clinical signs
While TR34/L98H and TR46/Y121F/T289A alterations account for the majority of azole resistance cases, a large diversity of cyp51A mutations has been associated with resistance (Verweij et al, 2016)
We prospectively investigated the prevalence of Aspergillus and the triazole resistance of A. fumigatus in sputum samples from CF patients using both phenotypic and molecular approaches
Summary
Aspergillus fumigatus is responsible for severe asthma or allergic bronchopulmonary aspergillosis (ABPA) in up to 15% of cystic fibrosis (CF) patients (Stevens et al, 2003; Pihet et al, 2009), though the significance of its detection is often questioned when there are no accompanying clinical signs. A. fumigatus resistant isolates to triazole have been increasingly reported, and proven associated with a markedly higher mortality rate (van der Linden et al, 2011). This decreased susceptibility is primarily due to mutations in the cyp51A gene encoding lanosterol 14α-demethylase, the enzyme involved in ergosterol biosynthesis (Mellado et al, 2001; Alcazar-Fuoli and Mellado, 2013). The current prevalence of triazole resistance in immunocompromised patients with invasive aspergillosis (IA) still remains low, estimated at ≤1% in France (Alanio et al, 2011; Guegan et al, 2018)
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