P414 Diagnostic allele-specific PCR for the identification of Candida auris clades and common resistance mutations

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PM

Candida auris (C. auris) is an opportunistic pathogenic yeast that emerged worldwide during the past decade. This fungal pathogen poses a significant public health threat due to common multidrug resistance (MDR), alarming hospital outbreaks, and frequent misidentification. Genomic analyses have identified five distinct clades that are linked to five geographic areas of origin and characterized by differences in several phenotypic traits such as virulence and drug resistance.

Typing of C. auris strains and the identification of clades can be a powerful tool in molecular epidemiology and might be of clinical importance by estimating outbreak and MDR potential. As C. auris has caused global outbreaks, including in low-income countries, typing C. auris strains quickly and inexpensively is highly valuable. We report five allele-specific multiplex polymerase chain reaction (AS-multiplex PCR) assays for the identification of C. auris and each of the five described clades of C. auris based on conserved mutations in the internal transcribed spacer (ITS) rDNA region and a clade-specific gene cluster. Additionally, we developed AS-PCR assays for the identification of SNPs in FKS1 and ERG11 that are commonly linked to echinocandin and azole resistance respectively.

This PCR method provides a fast, cheap, sequencing-free diagnostic tool for the identification of C. auris, C. auris clades, and common resistance mutations.

S2.5d Exploring multidrug resistance, fitness compensation, and collateral sensitivity in Candida auris : Fight fire with fire?

S2.5 Rare yeasts, September 21, 2022, 3:00 PM - 4:30 PM

Candida auris (C. auris) is a recently emerged human fungal pathogen of growing concern due to its ability to acquire extensive multidrug resistance (MDR) to all four antifungal drug classes. The unprecedented extent of MDR in C. auris, suggests accelerated resistance evolution, novel mechanisms of resistance, and/or potential fitness compensation. Despite being the first fungus to be officially considered an urgent antimicrobial resistance threat by the CDC (US), insights into the resistance mechanisms and evolutionary dynamics of C. auris are still scarce.

 

By using high-throughput in vitro experimental evolution with various antifungal drugs, we have obtained a library of resistant strains from four different clades. Through both genome and targeted sequencing, we have discovered novel mutations, especially for polyene resistance, which indicate new mechanisms of resistance and fitness compensation. For the validation of mutations, we have optimized a recyclable CRISPR/Cas9 tool for C. auris based on the C. albicans HIS-FLP system.

 

By mapping drug susceptibility responses of evolved strains across a library of several antifungals and repurposed drugs, we have discovered trends of cross-resistance and collateral sensitivity. Both phenomena have been extensively studied in tumors and bacteria but remain unexplored in fungi. In the light of these observations, we explore novel treatment schemes that prevent antifungal drug resistance development in C. auris and other pathogenic fungi.

The involvement of the Candida glabrata trehalase enzymes in stress resistance and gut colonization

Candida glabrata is an opportunistic human fungal pathogen and is frequently present in the human microbiome. It has a high relative resistance to environmental stresses and several antifungal drugs. An important component involved in microbial stress tolerance is trehalose. In this work, we characterized the three C. glabrata trehalase enzymes Ath1, Nth1 and Nth2. Single, double and triple deletion strains were constructed and characterized both in vitro and in vivo to determine the role of these enzymes in virulence. Ath1 was found to be located in the periplasm and was essential for growth on trehalose as sole carbon source, while Nth1 on the other hand was important for oxidative stress resistance, an observation which was consistent by the lower survival rate of the NTH1 deletion strain in human macrophages. No significant phenotype was observed for Nth2. The triple deletion strain was unable to establish a stable colonization of the gastrointestinal (GI) tract in mice indicating the importance of having trehalase activity for colonization in the gut.

Diagnostic Allele-Specific PCR for the Identification of Candida auris Clades

Candida auris is an opportunistic pathogenic yeast that emerged worldwide during the past decade. This fungal pathogen poses a significant public health threat due to common multidrug resistance (MDR), alarming hospital outbreaks, and frequent misidentification. Genomic analyses have identified five distinct clades that are linked to five geographic areas of origin and characterized by differences in several phenotypic traits such as virulence and drug resistance. Typing of C. auris strains and the identification of clades can be a powerful tool in molecular epidemiology and might be of clinical importance by estimating outbreak and MDR potential. As C. auris has caused global outbreaks, including in low-income countries, typing C. auris strains quickly and inexpensively is highly valuable. We report five allele-specific polymerase chain reaction (AS-PCR) assays for the identification of C. auris and each of the five described clades of C. auris based on conserved mutations in the internal transcribed spacer (ITS) rDNA region and a clade-specific gene cluster. This PCR method provides a fast, cheap, sequencing-free diagnostic tool for the identification of C. auris, C. auris clades, and potentially, the discovery of new clades.

A Linear 19-Mer Plant Defensin-Derived Peptide Acts Synergistically with Caspofungin against Candida albicans Biofilms

Public health problems are associated with device-associated biofilm infections, with Candida albicans being the major fungal pathogen. We previously identified potent antibiofilm combination treatment in which the antifungal plant defensin HsAFP1 is co-administered with caspofungin, the preferred antimycotic to treat such infections. In this study, we identified the smallest linear HsAFP1-derived peptide that acts synergistically with caspofungin or anidulafungin against C. albicans as HsLin06_18, a 19-mer peptide derived from the C-terminal part of HsAFP1. The [caspofungin + HsLin06_18] combination significantly reduced in vitro biofilm formation of Candida glabrata and C. albicans on catheters, as well as biofilm formation of a caspofungin-resistant C. albicans strain. The [caspofungin + HsLin06_18] combination was not cytotoxic and reduced biofilm formation of C. albicans in vivo using a subcutaneous rat catheter model, as compared to control treatment. Mode of action research on the [caspofungin + HsLin06_18] combination pointed to caspofungin-facilitated HsLin06_18 internalization and immediate membrane permeabilization. All these findings point to broad-spectrum antibiofilm activity of a combination of HsLin06_18 and caspofungin.