Diversity of clinical isolates of <i>Aspergillus terreus</i> in antifungal susceptibilities, genotypes and virulence in <i>Galleria mellonella</i> model: Comparison between respiratory and ear isolates

Abstract

<div><p>We analyzed the antifungal susceptibility profiles, genotypes, and virulence of clinical <i>Aspergillus terreus</i> isolates from six university hospitals in South Korea. Thirty one isolates of <i>A</i>. <i>terreus</i>, comprising 15 respiratory and 16 ear isolates were assessed. Microsatellite genotyping was performed, and genetic similarity was assessed by calculating the Jaccard index. Virulence was evaluated by <i>Galleria mellonella</i> survival assay. All 31 isolates were susceptible to itraconazole, posaconazole, and voriconazole, while 23 (74.2%) and 6 (19.4%) showed amphotericin B (AMB) minimum inhibitory concentrations (MICs) of ≤ 1 mg/L and > 4 mg/L, respectively. Notably, respiratory isolates showed significantly higher geometric mean MICs than ear isolates to AMB (2.41 <i>vs</i>. 0.48 mg/L), itraconazole (0.40 <i>vs</i>. 0.19 mg/L), posaconazole (0.16 <i>vs</i>. 0.08 mg/L), and voriconazole (0.76 <i>vs</i>. 0.31 mg/L) (all, <i>P</i> <0.05). Microsatellite genotyping separated the 31 isolates into 27 types, but the dendrogram demonstrated a closer genotypic relatedness among isolates from the same body site (ear or respiratory tract); in particular, the majority of ear isolates clustered together. Individual isolates varied markedly in their ability to kill infected <i>G</i>. <i>mellonella</i> after 72 h, but virulence did not show significant differences according to source (ear or respiratory tract), genotype, or antifungal susceptibility. The current study shows the marked diversity of clinical isolates of <i>A</i>. <i>terreus</i> in terms of antifungal susceptibilities, genotypes and virulence in the <i>G</i>. <i>mellonella</i> model, and ear isolates from Korean hospitals may have lower AMB or triazole MICs than respiratory isolates.</p></div