cyp51A-based mechanisms of Aspergillus fumigatus azole

72 Since the mid-1990s, a steady increase in the occurrence of itraconazole resistant Aspergillus 73 fumigatus isolates has been observed in clinical contexts leading to therapeutic failure in the 74 treatment of aspergillosis. This increase has been predominantly linked to a single allele of 75 the cyp51A gene, termed ‘TR/L98H’ which is thought to have arisen through the use of 76 agricultural azoles. 77 Here, we investigated the current epidemiology of triazole resistant A. fumigatus and 78 underlying cyp51A-mutations in clinical samples in Germany. 79 From a total of 527 samples, 17 (3.2%) showed elevated MIC0 values for at least one of the 80 three substances (itraconazole, voriconazole, and posaconazole) tested. The highest 81 prevalence of resistant isolates was observed in cystic fibrosis patients (5.2%). Among 82 resistant isolates, the TR/L98H mutation in cyp51A was most prevalent, but also isolates with 83 the G54W, M220I, and the novel F219C were found. The isolate with the G54W substitution 84 was highly resistant to both itraconazole and posaconazole, while all others showed high 85 level resistance only to itraconazole. For the remaining six isolates no mutations in cyp51A 86 were found, indicating the presence of other mechanisms. With the exception of the strains 87 carrying the F219C and M220I substitutions, many itraconazole resistant strains also showed 88 cross resistance to voriconazole and posaconazole with moderately increased MIC0 values. 89 In conclusion, the prevalence of azole resistant A. fumigatus is lower in our clinical test set 90 than previously reported for other countries. Although the TR/L98H mutation frequently 91 occurs among triazole resistant strains in Germany, it is not the only resistance mechanism 92