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

<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

MICs of AMB and triazoles of 31 <i>A</i>. <i>terreus</i> isolates from respiratory and ear specimens.

<p>MICs of AMB and triazoles of 31 <i>A</i>. <i>terreus</i> isolates from respiratory and ear specimens.</p

Genetic relatedness by microsatellite analysis and virulence in the <i>G</i>. <i>mellonella</i> model of 15 respiratory and 16 ear isolates of <i>A</i>. <i>terreus</i> from six hospitals.

<p>Genetic relatedness by microsatellite analysis and virulence in the <i>G</i>. <i>mellonella</i> model of 15 respiratory and 16 ear isolates of <i>A</i>. <i>terreus</i> from six hospitals.</p

Antifungal susceptibilities, microsatellite genotypes and virulence of 31 <i>A</i>. <i>terreus</i> isolates from six hospitals in South Korea.

<p>Antifungal susceptibilities, microsatellite genotypes and virulence of 31 <i>A</i>. <i>terreus</i> isolates from six hospitals in South Korea.</p

Genetic relationships of 31 <i>A</i>. <i>terreus</i> isolates according to source.

<p>The dendrogram is based on a categorical analysis of seven microsatellite markers in combination with unweighted pairgroup method using the arithmetic average (UPGMA) clustering. The number on the tree indicates the branch length, showing the difference along a branch. All 31 isolates (R1 to R15 and E1 to E16) comprised 27 distinct genotypes (GT 1 to GT 27) by 7 microsatellite markers. However, when a cluster is defined as the isolation of two or more strains with a branch length distance of < 0.63, ear isolates comprise clusters II and V, and the respiratory isolates comprise clusters I, III, and IV, suggesting a closer genetic relatedness among isolates from the same body site (ear or respiratory tract). Five isolates (R7, R15, E1, E4, and R12) were unique to a single isolate, which did not cluster with other isolate as a branch length distance of < 0.63. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0186086#pone.0186086.t002" target="_blank">Table 2</a> for detailed information on each isolate.</p