Antifungal susceptibility of environmental versus clinical strains of Aspergillus flavus isolated in Argentina

HERMIDA ALAVA KS; BRITO DEVOTO T; SAUTUA F; GORDO M; SCANDIANI M; FORMENTO N; LUQUE A; CARMONA M; CUESTAS ML

Congreso; 17TH INFOCUS; 2019

Objectives: Invasive aspergillosis (IA) is rare in immunocompetent people but contributes to significant morbidity and mortality in immunosuppressed patients. Approximately 80% of IA is caused by Aspergillus fumigatus, followed by Aspergillus flavus (15-20% of cases). After azoles were introduced to treat A. fumigatus infections, reports of resistance started to emerge. Minimal inhibitory concentrations (MICs) remain the most valuable laboratory tool available to predict resistance and to select the best alternative for antifungal treatment. Recently, cyp51A mutations typical for environmental azole resistance acquisition (for example, TR34/L98H) have been described in A. fumigatus. These mutations can also be found in isolates recovered from patients. Many studies determining the susceptibility patterns of clinical strains of Aspergillus spp. are available, but very few have evaluated the susceptibility patterns of environmental strains, especially of Aspergillus non-fumigatus strains, such as A. flavus. The objective of this study was to determine the susceptibility profiles of environmental strains of A. flavus to amphotericin B (AMB), itraconazole (ITC), voriconazole (VRC) and posaconazole (PSC) and to compare them with the susceptibility profiles of clinical strains.Methods: Thirty-four A. flavus strains were studied (18 environmental and 16 clinical strains). Environmental strains were collected from bean and soybean seeds from Buenos Aires, Santa Fe and Entre Ríos, Argentina. Clinical strains were isolated from the upper respiratory tract of 9 patients with cystic fibrosis. Determination of the minimum Inhibitory Concentrations (MICs) for AMB, VCZ, PSC and ITC were performed according to CLSI M38-A2 protocols. The Cyp51c gene of those Aspergillus flavus with high MICs values was amplified by PCR and bi-directionally sequenced with specific primers to elucidate the presence of mutations associated to azole-resistance. Results: Amongst the environmental isolates, 89% of them (n=16) showed high MICs values for VCZ (≥2 ug/ml), and 11% of them (n=2) showed high MICs values for ITC (≥2 ug/ml). Amongst the clinical isolates, only 19% (n=3) displayed high MICs values for VCZ and 25% (n=4) for AMB (≥4 ug/ml). All results are summarized in table 1. Conclusion: To the best of our knowledge, this is the first report of antifungal screening of environmental strains of A. flavus in Argentina. Noteworthy, environmental strains of A. flavus showed increased resistance to VCZ in comparison to clinical strains. Susceptibility differences among environmental A. flavus isolates might explain native resistance to certain antifungals. In conclusion, our study demonstrates that azole resistance with an environmental signature is present in environments and patients from Argentina and that it should be further analyzed if mutations observed in the clinical settings are also observed in the environment, since analysis of the nucleotide sequences of cyp51c is still under process.