Azole-resistant Aspergillus fumigatus in the Italian environment

OBJECTIVES: Azole resistance in Aspergillus fumigatus environmental and clinical isolates is recognized as an emerging problem worldwide. The development of azole resistance may be environmentally driven because of the massive use of azole fungicides in agriculture and the mechanism of resistance is mostly related to mutations in the cyp51A gene. A. fumigatus azole resistance in the environment was previously documented in Northern Italy. The present study extended the research in the agricultural environment also in central and southern Italy and investigated the differences in the Italian geographical areas and in the different types of crops. RESULTS: A total of 177 soil samples collected in the period 2014-17 in 14 Italian regions were analyzed. A. fumigatus itraconazole resistant isolates grew in 16.9% of screened samples, namely 12.5% in the North, 15.2% in the Center and 24.1% in the South. The resistant isolates were from different cultivations, treated or officially not treated with azole fungicides. Sequencing of the cyp51A gene confirmed that the resistance was mainly associated with the TR34/L98H mutation (29/30 isolates); one isolate showed the G54E mutation. CONCLUSIONS: The risk for patients to acquire multi-azole-resistant strains from the environment could have a serious impact on the management of the life-threatening invasive infection. The rate of 16.9% found in Italy requires adequate monitoring of antifungal susceptibility of clinical isolates.