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

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

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.680060

DOI=10.3389/fmicb.2021.680060

ISSN=1664-302X

ABSTRACT=<sec><title>Background</title><p><italic>Stephanoascus ciferrii</italic> is a heterothallic ascomycetous yeast-like fungus. Recently, the concept of <italic>S. ciferrii</italic> complex has been proposed and it consists of <italic>S. ciferrii</italic>, <italic>Candida allociferrii</italic>, and <italic>Candida mucifera</italic>. We aimed to identify 32 strains of <italic>S. ciferrii</italic> 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.</p></sec><sec><title>Method</title><p>The 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 <italic>S. ciferrii</italic> 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.</p></sec><sec><title>Results</title><p>There were 10 strains of <italic>C. allociferrii</italic> (31.25%), six strains of <italic>C. mucifera</italic> (18.75%), and 16 strains of <italic>S. ciferrii</italic> (50%) in the 32 strains of <italic>S. ciferrii</italic> complex according to the sequencing of the ITS region. MALDI-TOF MS could identify <italic>S. ciferrii</italic> but showed no results for <italic>C. allociferrii</italic> and <italic>C. mucifera</italic>. 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, <italic>S. ciferrii</italic> and <italic>C. mucifera</italic> tended to have high fluconazole MICs compared with <italic>C. allociferrii</italic>. <italic>C. mucifera</italic> and <italic>C. allociferrii</italic> had relatively low flucytosine MICs while <italic>S. ciferrii</italic> owned high flucytosine MICs. Besides, <italic>C. mucifera</italic> tended to have a higher MIC value than <italic>S. ciferrii</italic> for amphotericin B and <italic>C. allociferrii</italic> for anidulafungin, micafungin, and caspofungin.</p></sec><sec><title>Conclusion</title><p>The antifungal susceptibility profiles of the three species of <italic>S. ciferrii</italic> complex had their own characteristics. Besides, more mass spectra of <italic>C. allociferrii</italic> and <italic>C. mucifera</italic> are needed to construct the reference database for <italic>S. ciferrii</italic> complex species, enabling MALDI-TOF MS to identify <italic>S. ciferrii</italic> complex at species level.</p></sec>