Acquired fluconazole resistance and genetic clustering in Diutina (Candida) catenulata from clinical samples

Céline Nourrisson, Maxime Moniot, Rose-Anne Lavergne, Estelle Robert, Virginie Bonnin, Ferry Hagen, Frédéric Grenouillet, Claudia Cafarchia, Geraldine Butler, Sophie Cassaing, Marcela Sabou, Patrice Le Pape, Philippe Poirier, Florent Morio

Research output: Contribution to journal/periodicalArticleScientificpeer-review

1 Citation (Scopus)

Abstract

OBJECTIVES: Diutina (Candida) catenulata is an ascomycetous yeast isolated from environmental sources and animals, occasionally infecting humans. The aim of this study is to shed light on the in vitro antifungal susceptibility and the genetic diversity of this opportunistic yeast.

METHODS: Forty-five D. catenulata strains isolated from various sources (including human and environmental) and originating from nine countries, were included. Species identification was obtained by MALDI-TOF mass spectrometry and confirmed by ITS rDNA barcoding. In vitro antifungal susceptibility was determined for seven systemic antifungals by gradient strip method after 48h incubation at 35°C by Etest® (Biomérieux) or Liofilchem® strips. Isolates exhibiting fluconazole MICs ≥8 μg/mL were investigated for mutations in the ERG11 gene. A novel microsatellite genotyping scheme consisting of four markers was developed to assess the genetic diversity.

RESULTS: MICs ranges for amphotericin B, caspofungin, micafungin, isavuconazole and posaconazole were [0.19-1], [0.094-0.5], [0.012-0.064], [0.003-0.047] and [0.006-0.032] μg/mL, respectively. By comparison, a broad range of MICs was noted for fluconazole (0.75 to >256 μg/mL), and voriconazole (0.012 to 0.38 mg/L), the higher values being observed among clinical strains. The Y132F amino acid substitution, associated with azole resistance in various Candida species (C. albicans, C. tropicalis, C. parapsilosis, C. orthopsilosis), was the main substitution identified. Although microsatellite typing showed extensive genetic diversity, most strains with high fluconazole MICs clustered together, suggesting human to human transmission or a common source of contamination.

CONCLUSIONS: The high rate of acquired fluconazole resistance among clinical isolates of D. catenulata is of concern. We highlight a link between the genetic diversity of D. catenulata and its antifungal resistance patterns, suggesting possible clonal transmission of resistant isolates.

Original languageEnglish
JournalClinical Microbiology and Infection
DOIs
Publication statusE-pub ahead of print - 06 Oct 2022

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