Abstract
In recent years acquired azole resistance in Aspergillus fumigatus has been increasingly reported and a dominant mechanism of resistance (TR34/L98H) was found in clinical and environmental isolates. The aim of the present study was to investigate the prevalence of azole resistance in environmental A. fumigatus isolates collected in northern Italy. A. fumigatus grew from 29 of 47 soil samples analysed. Azole-resistant isolates were detected in 13% (6/47) of the soil samples and in 21% (6/29) of the soil samples containing A. fumigatus. High minimal inhibitory concentrations (MIC) of itraconazole (≥16 mg/L) and posaconazole (≥0.5 mg/L) were displayed by nine isolates from six different soil samples, namely apple orchard (1 sample), rose pot compost (2 samples), and cucurbit yields (3 samples). Seven isolates had a MIC=2 mg/L of voriconazole. Seven of nine itraconazole and posaconazole resistant isolates harboured the same TR34/L98H mutation of cyp51A. These findings, together with the occurrence of resistant clinical isolates, suggest that azole resistance should be considered in primary patient care.
Highlights
Aspergillus fumigatus is a filamentous fungus that causes a broad spectrum of diseases
Seven isolates showed an intermediate susceptibility to voriconazole (MIC =2 mg/L) by broth microdilution method according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) (Table 2)
The dominance of the TR34/L98H resistance mechanism in unrelated clinical isolates in a large Dutch culture collection suggested that isolates with this mechanism might be present in the environment, favoured by azole fungicides used in agriculture [20]
Summary
Aspergillus fumigatus is a filamentous fungus that causes a broad spectrum of diseases. Invasive lifethreatening infection affects subjects with compromised immune system, mainly patients with haematological malignancies, recipients of haematopoietic stem cells or solid organ transplantation, or patients under prolonged treatment with steroids. Chronic aspergillosis occurs in patients with pre-existing pulmonary or sinus disease, and locally invasive infection occurs as a result of trauma or surgery. A. fumigatus is ubiquitous in the soil and in decaying organic matter, and produces asexual spores (conidia) that are continuously dispersed in the air. Most of the patients develop aspergillosis following inhalation of conidia into the alveoli or the upper airways. Itraconazole, posaconazole and voriconazole, are increasingly used in the treatment and prophylaxis of aspergillosis [1]. Voriconazole is recommended as first line treatment for invasive aspergillosis in European and American guidelines [2,3,4,5]
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