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

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.

Stephanoascus ciferrii Complex: The Current State of Infections and Drug Resistance in Humans

“…Concerning the growth and morphological characteristics of the S. ciferrii complex, the fungus grows on Sabouraud dextrose agar (SDA) at different temperatures (22 • C, 27 • C, and 37 • C) after one week. Colonies are typically small, round, and milky-white-or cream-coloured, and can be hard, raised, and wrinkled or smooth [13,16,25,42]. Moreover, the S. ciferrii complex can grow on SDA with 0.1% cycloheximide, SDA with olive oil overlay, or 10% NaCl [36].…”

“…However, in the relatively few clinical reports available in the specific literature [17][18][19][20][21][22], this grouping was often not taken into account so that in various types of clinically documented fungal infections, species investigations were not performed [21][22][23][24] and the isolated fungal agent was indicated using various and non-univocal terminology. Identifying the S. ciferrii complex at the species level is of great importance in epidemiological studies and for the management of empirical antifungal therapy [25]. However, limiting data concerning the epidemiological, etiologic, and clinical aspects of the S. ciferrii complex are reported in the literature.…”

Complete Genome Sequence of Candida mucifera from an Otitis Media Patient

“…animal and clinical strains exhibited notable reduced uconazole susceptibility with minimal inhibitory concentration [MIC] values ranging from 32 to 128 mg/L) [3].…”

“…Gene annotation results of T. ciferrii strain CBS 4856 were used to train a new de novo prediction model for AUGUSTUS v3.3.2 and then utilized for structural annotation of our C. mucifera genome [11], and a total of 6533 genes were predicted. Due to the "intrinsically" reduced uconazole susceptibility in C. mucifera and other species of the T. ciferrii complex [3], we conducted an mutation analysis of the azole target Erg11p. We observed that position 499 of Erg11p amino acid sequence in C. mucifera isolate 17G1312 (GenBank accession no.…”

“…This species complex is composed of ascomycetous heterothallic yeasts, formerly referred to as the Stephanoascus ciferrii complex, and currently comprises three species, namely Trichomonascus ciferrii, Candida allociferrii, and C. mucifera [2]. C. mucifera is a rare human fungal pathogen, which has only been reported in China in chronic suppurative otitis media cases [3]. Additionally, this species has been detected in environmental and animal sources (https://wi.knaw.nl/page/fungal_display/3954) [4].…”