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

Eun Jeong Won,Soo Hyun Kim,Seung A Byun,Jee Seung Jung,Jong Hee Shin,Yeon-Jun Park,Soon-Pal Suh,Min Ji Choi,Myung Geun Shin,Kap-Hoon Han

doi:10.1371/journal.pone.0186086

Eun Jeong Won, Soo Hyun Kim + Show 8 more

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https://doi.org/10.1371/journal.pone.0186086

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Abstract

We analyzed the antifungal susceptibility profiles, genotypes, and virulence of clinical Aspergillus terreus isolates from six university hospitals in South Korea. Thirty one isolates of A. terreus, 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 Galleria mellonella 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 vs. 0.48 mg/L), itraconazole (0.40 vs. 0.19 mg/L), posaconazole (0.16 vs. 0.08 mg/L), and voriconazole (0.76 vs. 0.31 mg/L) (all, P <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 G. mellonella 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 A. terreus in terms of antifungal susceptibilities, genotypes and virulence in the G. mellonella model, and ear isolates from Korean hospitals may have lower AMB or triazole MICs than respiratory isolates.

Highlights

The importance of invasive fungal infections caused by Aspergillus species has increased among immunocompromised patients due to their considerably high rates of morbidity and mortality [1, 2]
A. terreus is known to be intrinsically resistant to amphotericin B (AMB) [9,10,11,12,13], our findings suggest that AMB susceptible clinical isolates of A. terreus are not uncommon, especially in ear specimens
We report for the first time that isolates from the same body site have greater genetic similarity, and respiratory isolates are significantly less susceptible to AMB and triazoles than ear isolates

Summary

Introduction

The importance of invasive fungal infections caused by Aspergillus species has increased among immunocompromised patients due to their considerably high rates of morbidity and mortality [1, 2]. Invasive pulmonary aspergillosis caused by A. terreus has been highlighted because it could rapidly progress in immunocompromised patients despite amphotericin B (AMB) therapy [3,4,5,6]. Unusually AMB-susceptible A. terreus isolates have become a focus of attention, and the relationship between the AMB susceptibility and virulence of A. terreus isolates was investigated using mouse or Galleria mellonella models [14,15,16] These studies included fewer than five isolates from respiratory specimens, they showed that isolates with an AMB minimum inhibitory concentration (MIC) of 0.5 mg/L were more virulent than resistant isolates with an AMB MIC of > 4 mg/L [14,15,16]

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