Azole resistant Aspergillus fumigatus: What you need to know

Aspergillosis is one of the most common fungal infections. The predominant cause of aspergillosis is the species Aspergillus fumigatus. There have been increasing reports of A. fumigatus isolates that are resistant to azole antifungals. The predominant causes of this resistance are environmentally acquired mutations in the target gene, CYP51A, known as TR₃₄/L98H and TR₄₆/Y121F/T289A. They consist of a tandem repeat in the promoter region (TR) and one or two amino acid changes in the protein sequence, respectively. Unfortunately, the capacity in the United States for mold antifungal susceptibility testing is limited, so the extent of azole resistance in clinical practice is largely unknown. This review discusses the causes and implications of azole-resistant A. fumigatus and the role that antifungal susceptibility testing might play in its identification.