Candida auris Clinical Isolates from South Korea: Identification, Antifungal Susceptibility, and Genotyping

Abstract

Candida auris is an emerging worldwide fungal pathogen. Over the past 20 years, 61 patient isolates of C. auris (4 blood and 57 ear) have been obtained from 13 hospitals in Korea. Here, we reanalyzed those molecularly identified isolates using two matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) systems, including Biotyper and Vitek MS, followed by antifungal susceptibility testing, sequencing of the ERG11 gene, and genotyping. With a research-use-only (RUO) library, 83.6% and 93.4% of the isolates were correctly identified by Biotyper and Vitek MS, respectively. Using an in vitro diagnostic (IVD) library of Vitek MS, 96.7% of the isolates were correctly identified. Fluconazole-resistant isolates made up 62.3% of the isolates, while echinocandin- or multidrug-resistant isolates were not found. Excellent essential (within two dilutions, 96.7%) and categorical agreements (93.4%) between the Clinical and Laboratory Standards Institute (CLSI) and Vitek 2 (AST-YS07 card) methods were observed for fluconazole. Sequencing ERG11 for all 61 isolates revealed that only 3 fluconazole-resistant isolates showed the Erg11p amino acid substitution K143R. All 61 isolates showed identical multilocus sequence typing (MLST). Pulsed-field gel electrophoresis (PFGE) analyses revealed that both blood and ear isolates had the same or similar patterns. These results show that MALDI-TOF MS and Vitek 2 antifungal susceptibility systems can be reliable diagnostic tools for testing C. auris isolates from Korean hospitals. The Erg11p mutation was seldom found among Korean isolates of C. auris, and multidrug resistance was not found. Both MLST and PFGE analyses suggest that these isolates are genetically similar.

External Quality Assessment Evaluating the Ability of Dutch Clinical Microbiological Laboratories to Identify Candida auris

“…With the Bruker MALDI Biotyper and a library that contained only three C. auris spectra, a study showed that all 90 (Indian) isolates could be identified as C. auris (South Asian clade I) [22]. A second study showed that 83.6% and 98.4% of 61 isolates could be identified as C. auris, with cutoff scores of >1.7 and <1.7, respectively (East Asia clade II) [45]. Another study used the Bruker MALDI Biotyper to identify isolates belonging to the African clade III [46].…”

“…Using the bioMérieux Vitek MS IVD library version 3.2, 59/61 (96.7%) of Korean isolates could be correctly identified, with a confidence value of ≥75 (East Asian clade II). In addition, it has been shown that 10 CDC reference strains belonging to four clades could be correctly identified by the bioMérieux Vitek MS and Bruker MALDI Biotyper systems [45]. Information about the performance of the identification methods of the possible 5th clade of C. auris is not yet available [43].…”

Candida auris: A Decade of Understanding of an Enigmatic Pathogenic Yeast

“…Biofilm formation was initially disregarded in a study using isolates from the East Asian clade [6]. Interestingly, this clade appears to display some unique behavioral patterns in comparison to other clades, including lower fluconazole resistance rates and high incidence of causing otitis [46]. In addition, these isolates rarely cause invasive infections and large-scale outbreaks, which could explain the inability of these organisms to form biofilms [47].…”

<i>Candida auris</i>: Problems in Diagnostics and Management

“…Этот грибок является причиной нозокомиальных инфекций, при которых уровень летальности достигает 72% [10][11][12]. Такой устрашающий прогноз инфекции C. auris связан с тем, что грибок обладает множественной лекарственной устойчивостью, которая характеризуется резистентностью к трем и более группам антимикотических препаратов [10,13,14]. Особую проблему составляют устойчивость C. auris к факторам внешней среды и сложность обнаружения при диагностических исследованиях.…”