Prevalence and in vitro antifungal susceptibility of cryptic species of the genus Aspergillus isolated in clinical samples

Abstract

Introduction: The genus Aspergillus contains more than 300 species, which are divided into closely related groups called sections. Molecular studies have revealed numerous cryptic species within different sections of this genus, which have different profiles of antifungal susceptibility and lack diagnostic morphological features. However, there are few studies on the prevalence and in vitro antifungal susceptibility of the cryptic species of this genus. The aim of this study was to investigate the distribution of Aspergillus spp. among clinical samples, and to study their in vitro susceptibility to different antifungal drugs.

Method: Over a period of 2-years (2014-2015), a total of 379 strains of the genus Aspergillus were isolated. Most of the isolates were classified as respiratory colonizations; no cases of invasive aspergillosis were found. The strains were identified by MALDI-TOF mass spectrometry, and susceptibility testing was performed by the EUCAST reference procedure.

Results: Twenty species belonging to 8 sections were identified, being A. fumigatus the most prevalent (44.1%). The prevalence of cryptic species was 15.3%, with a clear predominance of A. tubingensis. Among the tested antifungal drugs, amphotericin B was the less active in vitro, followed by triazole drugs and echinocandins. The cryptic species had minimun inhibitory concentrations (MICs) higher than the corresponding type species.

Conclusions: Accurate identification of the genus Aspergillus at the species level and in vitro antifungal susceptibility testing are necessary because, as it has been shown, some species of this genus may show resistance profiles against available antifungal drugs.

Keywords: Antifungal susceptibility testing; Aspergillus; Cryptic species; Especies crípticas; Prevalence; Prevalencia; Prueba de sensibilidad antifúngica.