Identification and Antifungal Susceptibility Analysis of Stephanoascus ciferrii Complex Species Isolated From Patients With Chronic Suppurative Otitis Media.

Yili Chen,Yaqin Peng,Pingjuan Liu,Penghao Guo,Kang Liao,Zhongwen Wu,Yuting He

doi:10.3389/fmicb.2021.680060

Abstract

BackgroundStephanoascus ciferrii is a heterothallic ascomycetous yeast-like fungus. Recently, the concept of S. ciferrii complex has been proposed and it consists of S. ciferrii, Candida allociferrii, and Candida mucifera. We aimed to identify 32 strains of S. ciferrii complex isolated from patients with chronic suppurative otitis media (CSOM) at the species level and analyze the morphology and antifungal susceptibility profiles of the three species.MethodThe sequencing of the internal transcribed spacer (ITS) region and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to identify S. ciferrii complex species. The SARAMIS software was used for cluster analysis of the mass spectra. All the strains were cultured on Sabouraud dextrose agar (SDA) and CHROM plates for 7 days. In the meantime, colonies of the 32 strains went through Gram staining. The Sensititre YeastOne YO10 colorimetric panel was used for the antifungal susceptibility analysis.ResultsThere were 10 strains of C. allociferrii (31.25%), six strains of C. mucifera (18.75%), and 16 strains of S. ciferrii (50%) in the 32 strains of S. ciferrii complex according to the sequencing of the ITS region. MALDI-TOF MS could identify S. ciferrii but showed no results for C. allociferrii and C. mucifera. The cluster analysis of the mass spectra by SARAMIS indicated that the MALDI-TOF MS could distinguish the three species. The morphology characteristics of the three species were similar. As for antifungal susceptibility, S. ciferrii and C. mucifera tended to have high fluconazole MICs compared with C. allociferrii. C. mucifera and C. allociferrii had relatively low flucytosine MICs while S. ciferrii owned high flucytosine MICs. Besides, C. mucifera tended to have a higher MIC value than S. ciferrii for amphotericin B and C. allociferrii for anidulafungin, micafungin, and caspofungin.ConclusionThe antifungal susceptibility profiles of the three species of S. ciferrii complex had their own characteristics. Besides, more mass spectra of C. allociferrii and C. mucifera are needed to construct the reference database for S. ciferrii complex species, enabling MALDI-TOF MS to identify S. ciferrii complex at species level.

Highlights

Stephanoascus ciferrii is a heterothallic ascomycetous yeast-like fungus, which is a teleomorph of Candida ciferrii (de Gentile et al, 1991; Warren et al, 2018)
By internal transcribed spacer (ITS) region alignment in the MycoBank, the 32 yeast strains of S. ciferrii complex were classified at species level
The S. ciferrii and C. mucifera tended to have high fluconazole MICs compared with C. allociferrii (p < 0.05)

Summary

Introduction

Stephanoascus ciferrii ( called Candida ciferrii or Trichomonascus ciferrii) is a heterothallic ascomycetous yeast-like fungus, which is a teleomorph of Candida ciferrii (de Gentile et al, 1991; Warren et al, 2018). As for a rare kind of opportunistic pathogenic fungus, identifying S. ciferrii complex at species level is of great importance in epidemiological studies and the management of empirical antifungal therapy. Because of its minimal hands-on and turnaround time, low costs, and high accuracy, MALDI-TOF MS has been widely used in the identification of bacterial and fungi species clinically (Angeletti and Ciccozzi, 2019; Cuenod et al, 2021). The concept of S. ciferrii complex has been proposed and it consists of S. ciferrii, Candida allociferrii, and Candida mucifera. We aimed to identify 32 strains of S. ciferrii complex isolated from patients with chronic suppurative otitis media (CSOM) at the species level and analyze the morphology and antifungal susceptibility profiles of the three species

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