Comparative activity of posaconazole and systemic azole agents against clinical isolates of filamentous fungi from a global surveillance programme

Objectives The activity of mould-active azoles was evaluated against 397 filamentous fungi causing invasive mould infections (IMI) worldwide. In addition, a tentative posaconazole epidemiological cut-off value (ECV) against Aspergillus fumigatus was investigated. Methods Isolates were susceptibility tested by the CLSI reference broth microdilution methods. Species identification was confirmed by MALDI-TOF and/or sequencing analysis. Results Aspergillus spp. (81.9%) remained the most common organism causing IMI worldwide; approximately two-thirds of Aspergillus spp. recovered were A. fumigatus. In general, more than 90% of 220 A. fumigatus isolates were wild type (WT) to all mould-active azoles, except itraconazole (84.5% WT). The voriconazole non-susceptible (NS) A. fumigatus rate was 7.7% overall and was higher in Europe (12.9%) than in the other regions (0%–5.8%). Posaconazole (MIC50/MIC90, 0.25/0.5 mg/L) showed similar or slightly higher activity than voriconazole (MIC50/MIC90, 0.5/0.5 mg/L) and isavuconazole (MIC50/MIC90, 0.5/1 mg/L) against A. fumigatus. The mould-active azoles displayed similar activity against non-fumigatus Aspergillus (WT rates >93%), but differences were observed among the main species/sections. Posaconazole, voriconazole, and isavuconazole inhibited at their respective ECVs 100%, 97.0%, and 100% of A. section Nigri; 100%, 100%, and 93.8% of A. section Terrei; and 97.3%, 100%, and 100% of A. section Flavi isolates. Posaconazole displayed potency greater than or equal to the other azoles against the Mucorales group and Scedosporium spp. Conclusions Posaconazole and other mould-active azoles showed good activity against Aspergillus spp. causing IMI, but clinicians should be aware of regional rates of voriconazole-NS A. fumigatus.