Surveillance for Azole-Resistant Aspergillus fumigatus in a Centralized Diagnostic Mycology Service, London, United Kingdom, 1998–2017

Abstract

<b>Background/Objectives:</b> <i>Aspergillus fumigatus</i> is the leading cause of invasive aspergillosis. Treatment is hindered by the emergence of resistance to triazole antimycotic agents. Here, we present the prevalence of triazole resistance among clinical isolates at a major centralized medical mycology laboratory in London, United Kingdom, in the period 1998-2017. <b>Methods:</b> A large number (<i>n</i> = 1469) of clinical <i>A. fumigatus</i> isolates from unselected clinical specimens were identified and their susceptibility against three triazoles, amphotericin B and three echinocandin agents was carried out. All isolates were identified phenotypically and antifungal susceptibility testing was carried out by using a standard broth microdilution method. <b>Results:</b> Retrospective surveillance (1998-2011) shows 5/1151 (0.43%) isolates were resistant to at least one of the clinically used triazole antifungal agents. Prospective surveillance (2015-2017) shows 7/356 (2.2%) isolates were resistant to at least one triazole antifungals demonstrating an increase in incidence of triazole-resistant <i>A. fumigatus</i> in our laboratory. Among five isolates collected from 2015 to 2017 and available for molecular testing, three harbored TR₃₄/L98H alteration in the <i>cyp51A</i> gene that are associated with the acquisition of resistance in the non-patient environment. <b>Conclusion:</b> These data show that historically low prevalence of azole resistance may be increasing, warranting further surveillance of susceptible patients.