Are We Ready for Nosocomial Candida auris Infections? Rapid Identification and Antifungal Resistance Detection Using MALDI-TOF Mass Spectrometry May Be the Answer.

Elena De Carolis,Marilisa La Rosa,Federica Marchionni,Anuradha Chowdhary,Brunella Posteraro,Jacques F Meis,Maurizio Sanguinetti

doi:10.3389/fcimb.2021.645049

Abstract

The occurrence of multidrug-resistant Candida auris isolates and the increased mortality associated with invasive infections or outbreaks due to this Candida species have been reported in many healthcare settings. Therefore, accurate and rapid identification at the species level of clinical C. auris isolates as well as their timely differentiation as susceptible or resistant to antifungal drugs is mandatory. Aims of the present study were to implement the MALDI-TOF mass spectrometry (MS) Bruker Daltonics Biotyper® database with C. auris spectrum profiles and to develop a fast and reproducible MS assay for detecting anidulafungin (AFG) resistance in C. auris isolates. After creation of main C. auris spectra, a score-oriented dendrogram was generated from hierarchical cluster analysis, including spectra of isolates from C. auris and other Candida (C. glabrata, C. guilliermondii, C. haemulonii, C. lusitaniae, and C. parapsilosis) or non-Candida (Rhodotorula glutinis) species. Cluster analysis allowed to group and classify the isolates according to their species designation. Then, a three-hour incubation antifungal susceptibility testing (AFST) assay was developed. Spectra obtained at null, intermediate, or maximum AFG concentrations were used to create composite correlation index matrices for eighteen C. auris isolates included in the study. All six resistant C. auris isolates were detected as resistant whereas 11 of 12 susceptible C. auris isolates were detected as susceptible by the MS-AFST assay. In conclusion, our MS-based assay offers the possibility of rapidly diagnosing and appropriately treating patients with C. auris infection.

Highlights

The fungal pathogen Candida auris has emerged over a decade ago in East Asia and, since multidrug-resistant C. auris isolates causing nosocomial outbreaks have been isolated in many countries worldwide (Du et al, 2020)
Yeast cells were suspended in 10% formic acid and vortexed; one μL of lysate was placed on the MALDI target plate to obtain 12 technical replicates, which were overlaid each with one μL of absolute ethanol before allowing cocrystallization with the a-cyano-4-hydroxycinnamic acid matrix (Bruker Daltonics)
As of November 2019, we identified in our hospital a bloodstream infection due to C. auris, which represented the first case of invasive C. auris infection detected in Central Italy where the hospital is located

Summary

INTRODUCTION

The fungal pathogen Candida auris has emerged over a decade ago in East Asia and, since multidrug-resistant C. auris isolates causing nosocomial outbreaks have been isolated in many countries worldwide (Du et al, 2020). While echinocandins are regarded as first-line treatment for C. auris infections, echinocandin-resistant isolates of C. auris may occur in patients during antifungal treatment (Park et al, 2019; Novak et al, 2020), calling for repeated susceptibility testing in order to monitor possible therapeutic failures. Consistent with these observations, we implemented the MALDI Biotyper® database (Bruker Daltonics, Bremen, Germany) with mass spectrum profiles from C. auris isolates, and we developed a fast and reproducible MALDI-TOF MS based assay to detect resistance to the echinocandin anidulafungin in C. auris isolates

MATERIALS AND METHODS

RESULTS AND DISCUSSION

DATA AVAILABILITY STATEMENT