Background: The opportunistic molds Aspergillus spp. have been for years classified according to macro-microscopic examination. In this setting, Aspergillus niger , the third species responsible for invasive aspergillosis (Steinbach et al, J Infection 2012) and the most prevalent agent of otomycosis has been considered as a uniform species. However, the advent of molecular methods has enabled to uncover many cryptic species (e.g. A. tubengensis or A. brasiliensis ) formerly identified as niger . These species have been recently reclassified into the Aspergillus section Nigri . However, little is known among the section Nigri concerning i. the species repartition and ii. the antifungal susceptibility pattern. Importantly, antifungal drugs may exhibit different activity against two different species of the same section (Howard SJ et al, AAC 2011). Actually, no data are available in France concerning the accurate repartition and antifungal susceptibility of Aspergillus section Nigri clinical isolates. As for Europe, reports are very scarce and involved few isolates (Vermeulen et al, Clin Microbiol Infect 2014). Our work aimed at better understanding the Aspergillus section Nigri species repartition as well as the susceptibility pattern of each cryptic species toward antifungal drugs.
Material/methods: A total of 70 isolates from clinical samples collected in 4 teaching hospitals in France (Paris, Grenoble, Nantes, Nîmes) and identified phenotypically as A. niger were analyzed. Each isolate was identified by molecular approach, i.e. sequencing part of the calmodulin and β- tubulin genes. Minimal Inhibitory Concentrations (MICs) of azoles drugs (voriconazole, posaconazole, isavuconazole) and amphotericin B were determined by EUCAST method.
Results: Aspergillus tubengensis was the most prevalent species (n=39, 55.7%) and was found in all centres. Aspergillus awamori accounted for 28.6% of the isolates (n=20) and Aspergillus niger for only 14.3% (n=10). One isolate of Aspergillus brasiliensis was also identified. MICs were very variable according to the species. Azoles drugs presented higher MICs for A. tubengensis than for A. awamori (Table 1). Of note MICs of isavuconazole were higher than MICs values for either voriconazole or posaconazole. No statistically significant difference was observed concerning MICs values of amphotericin B.
Conclusions: Among the section Nigri , A. tubengensis is the most prevalent species. Our results indicate the importance of the molecular identification of the Aspergillus section Nigri isolates to improve the epidemiological knowledge and underlines the necessity of performing MICs determination.
Full conference title:
- ECCMID 27th (2017)