Mechanism of azole resistance in Candida glabrata isolates from India: clinical vs. induced perspectives

S5.1 Antifungal resistance, September 22, 2022, 3:00 PM - 4:30 PM ObjectivesIn tropical countries, the azole resistance in Candida tropicalis is on the rise. There are limited studies available regarding the azole resistance mechanisms in C. tropicalis. This study was designed to understand the molecular mechanisms of azole resistance in C. tropicalis by using genetic and bioinformatics approaches.MethodsA total of 32 azole-resistant (R) and 10 azole-susceptible (S) clinical isolates of C. tropicalis were included in this study. All the isolates were subjected to complete gene sequencing of azole target genes including ERG11 to analyze the mutations which could lead the azole resistance. Four fragments were amplified, sequenced, and aligned to get full-length ERG11 gene. Inducible expression analysis of 17 other genes potentially associated with azole resistance was also evaluated. Homology modeling and molecular docking analysis were performed to study the effect of amino acid alterations in mediating azole resistance.ResultsOf the 32 resistant isolates, 12 (37.5%) showed A395T and C461T mutations in the ERG11 gene. The mean overexpression of CDR1, CDR3, TAC1, ERG1, ERG2, ERG3, ERG11, UPC2, and MKC1 in resistant isolates without mutation (R-WTM) was significantly higher (P <.05) than those with mutation (R-WM) and the sensitive isolates (3.2-11 vs. 0.2-2.5, and 0.3-2.2 folds, respectively). Although the R-WTM and R-WM had higher (P <.05) CDR2 and MRR1 expression compared to S isolates, noticeable variation was not seen among the other genes. Protein homology modeling and molecular docking revealed that the mutations in the ERG11 gene were responsible for structural alteration and low binding efficiency between ERG11p and ligands. Isolates with ERG11 mutations also presented A220C in ERG1 and together T503C, G751A mutations in UPC2.ConclusionsNonsynonymous mutations in the ERG11 gene and coordinated overexpression of various genes including different transporters, ergosterol biosynthesis pathway, transcription factors, and stress-responsive genes are associated with azole resistance in clinical isolates of C. tropicalis.

The increasing use of azole antifungals for the treatment of mucosal and systemic Candida glabrata infections has resulted in the selection and/or emergence of resistant strains. The main mechanisms of azole resistance include alterations in the C. glabrata ERG11 gene (CgERG11), which encodes the azole target enzyme, and upregulation of the CgCDR1 and CgCDR2 genes, which encode efflux pumps. In the present study, we evaluated these molecular mechanisms in 29 unmatched clinical isolates of C. glabrata, of which 20 isolates were resistant and 9 were susceptible dose dependent (S-DD) to fluconazole. These isolates were recovered from separate patients during a 3-year hospital survey for antifungal resistance. Four of the 20 fluconazole-resistant isolates were analyzed together with matched susceptible isolates previously taken from the same patients. Twenty other azole-susceptible clinical C. glabrata isolates were included as controls. MIC data for all the fluconazole-resistant isolates revealed extensive cross-resistance to the other azoles tested, i.e., itraconazole, ketoconazole, and voriconazole. Quantitative real-time PCR analyses showed that CgCDR1 and CgCDR2, alone or in combination, were upregulated at high levels in all but two fluconazole-resistant isolates and, to a lesser extent, in the fluconazole-S-DD isolates. In addition, slight increases in the relative level of expression of CgSNQ2 (which encodes an ATP-binding cassette [ABC] transporter and which has not yet been shown to be associated with azole resistance) were seen in some of the 29 isolates studied. Interestingly, the two fluconazole-resistant isolates expressing normal levels of CgCDR1 and CgCDR2 exhibited increased levels of expression of CgSNQ2. Conversely, sequencing of CgERG11 and analysis of its expression showed no mutation or upregulation in any C. glabrata isolate, suggesting that CgERG11 is not involved in azole resistance. When the isolates were grown in the presence of fluconazole, the profiles of expression of all genes, including CgERG11, were not changed or were only minimally changed in the resistant isolates, whereas marked increases in the levels of gene expression, particularly for CgCDR1 and CgCDR2, were observed in either the fluconazole-susceptible or the fluconazole-S-DD isolates. Finally, known ABC transporter inhibitors, such as FK506, were able to reverse the azole resistance of all the isolates. Together, these results provide evidence that the upregulation of the CgCDR1-, CgCDR2-, and CgSNQ2-encoded efflux pumps might explain the azole resistance in our set of isolates.

BackgroundCandida glabrata causes significant medical problems in immunocompromised patients. Many strains of this yeast are intrinsically resistant to azole antifungal agents, and treatment is problematic, leading to high morbidity and mortality rates in immunosuppressed individuals. The primary goal of this study was to investigate the genes involved in the drug resistance of clinical isolates of C. glabrata.MethodsThe clinical isolates of C. glabrata were collected in an epidemiological survey of candidal infection in immunocompromised patients and consisted of four fluconazole and itraconazole resistant isolates, two fluconazole and itraconazole sensitive isolates, and C. glabrata CBS 138 as reference strain. Antifungal susceptibility patterns of the organisms were determined beforehand by the Clinical and Laboratory Standards Institute (CLSI). The potential gene(s) implicated in antifungal resistance were investigated using complementary DNA- Amplified Fragment Length Polymorphism (cDNA-AFLP). Semi-quantitative RT-PCR was carried out to evaluate the expression of gene(s) in resistant isolates as compared to sensitive and reference strains.Results and conclusionsThe aldo-keto-reductase superfamily (AKR gene) was upregulated in the resistant clinical isolates as assessed by cDNA-AFLP. Semi-quantitative RT-PCR revealed AKR mRNA expression approximately twice that seen in the sensitive isolates. Overexpression of the AKR gene was associated with increased fluconazole and itraconazole resistance in C. glabrata. The data suggest that upregulation of the AKR gene might give a new insight into the mechanism of azole resistance.

Isavuconazole is a novel, broad-spectrum, antifungal azole. In order to evaluate its interactions with known azole resistance mechanisms, isavuconazole susceptibility among different yeast models and clinical isolates expressing characterized azole resistance mechanisms was tested and compared to those of fluconazole, itraconazole, posaconazole, and voriconazole. Saccharomyces cerevisiae expressing the Candida albicans and C. glabrata ATP binding cassette (ABC) transporters (CDR1, CDR2, and CgCDR1), major facilitator (MDR1), and lanosterol 14-α-sterol-demethylase (ERG11) alleles with mutations were used. In addition, pairs of C. albicans and C. glabrata strains from matched clinical isolates with known azole resistance mechanisms were investigated. The expression of ABC transporters increased all azole MICs, suggesting that all azoles tested were substrates of ABC transporters. The expression of MDR1 did not increase posaconazole, itraconazole, and isavuconazole MICs. Relative increases of azole MICs (from 4- to 32-fold) were observed for fluconazole, voriconazole, and isavuconazole when at least two mutations were present in the same ERG11 allele. Upon MIC testing of azoles with clinical C. albicans and C. glabrata isolates with known resistance mechanisms, the MIC90s of C. albicans for fluconazole, voriconazole, itraconazole, posaconazole, and isavuconazole were 128, 2, 1, 0.5, and 2 μg/ml, respectively, while in C. glabrata they were 128, 2, 4, 4, and 16 μg/ml, respectively. In conclusion, the effects of azole resistance mechanisms on isavuconazole did not differ significantly from those of other azoles. Resistance mechanisms in yeasts involving ABC transporters and ERG11 decreased the activity of isavuconazole, while MDR1 had limited effect.

Infections with the opportunistic yeast Candida albicans are frequently treated with the first-line drug fluconazole, which inhibits ergosterol biosynthesis. An alarming problem in clinics is the development of resistances against this azole, especially during long-term treatment of patients. Well-known resistance mechanisms include mutations in the zinc cluster transcription factors (ZnTFs) Mrr1 and Tac1, which cause an overexpression of efflux pump genes, and Upc2, which results in an overexpression of the drug target. C. albicans strains with such gain-of-function mutations (GOF) have an increased drug resistance conferring a selective advantage in the presence of the drug. It was previously shown that this advantage comes with a fitness defect in the absence of the drug. This was observed in different conditions and is presumably caused by a deregulated gene expression. One aim of the present study was to examine whether C. albicans can overcome the costs of drug resistance by further evolution. Therefore, the relative fitness of clinical isolates with one or a combination of different resistance mutations in Mrr1, Tac1 and/or Upc2 was analyzed in competition with the matched fluconazole-susceptible partner. Most fluconazole-resistant isolates had a decreased fitness in competition with their susceptible partner in vitro in rich medium. In contrast, three fluconazole-resistant strains with Mrr1 resistance mutations did not show a fitness defect in competition with their susceptible partner. In addition, the fitness of four selected clinical isolate pairs was examined in vivo in mouse models of gastrointestinal colonization (GI) and disseminated infection (IV). In the GI model all four fluconazole-resistant strains were outcompeted by their respective susceptible partner. In contrast, in the IV model only one out of four fluconazole-resistant isolates did show a slight fitness defect in competition with its susceptible partner during infection of the kidneys. It can be stated, that in the present work the in vitro fitness did not reflect the in vivo fitness and that the overall fitness was dependent on the tested conditions. In conclusion, C. albicans cannot easily overcome the costs of drug resistance caused by a deregulated gene expression. In addition to GOFs in Mrr1, Tac1 and Upc2, resistance mutations in the drug target Erg11 are a further key fluconazole resistance mechanism of C. albicans. Clinical isolates often harbor several resistance mechanisms, as the fluconazole resistance level is further increased in strains with a combination of different resistance mutations. In this regard, the question arises of how strains with multiple resistance mechanisms evolve. One possibility is that strains acquire mutations successively. In the present study it was examined whether highly drug-resistant C. albicans strains with multiple resistance mechanisms can evolve by parasexual recombination as another possibility. In a clonal population, cells with individually acquired resistance mutations could combine these advantageous traits by mating. Thereupon selection could act on the mating progeny resulting in even better adapted derivatives. Therefore, strains heterozygous for a resistance mutation and the mating type locus (MTL) were grown in the presence of fluconazole. Derivatives were isolated, which had become homozygous for the resistance mutation and at the same time for the MTL. This loss of heterozygosity was accompanied by increased drug resistance. In general, strains which are homozygous for one of both MTL configurations (MTLa and MTLα) can switch to the opaque phenotype, which is the mating-competent form of the yeast, and mate with cells of the opposite MTL. In the following, MTLa and MTLα homozygous strains in the opaque phenotype were mated in all possible combinations. The resulting mating products with combined genetic material from both parents did not show an increased drug resistance. Selected products of each mating cross were passaged with stepwise increasing concentrations of fluconazole. The isolated progeny showed high levels of drug resistance and loss of wild-type alleles of resistance-associated genes. In conclusion, selective pressure caused by fluconazole exposure selects for resistance mutations and at the same time induces genomic rearrangements, resulting in mating competence. Therefore, in a clonal population, cells with individually acquired resistance mutations can mate with each other and generate mating products with combined genetic backgrounds. Selection can act on these mating products and highly drug-resistant und thus highly adapted derivatives can evolve as a result. In summary, the present study contributes to the current understanding of the evolution of antifungal drug resistance by elucidating the effect of resistance mutations on the fitness of the strains in the absence of the drug selection pressure and investigates how highly drug-resistant strains could evolve within a mammalian host.

Limited knowledge exists on the virulence factors of Candida tropicalis and the mechanisms of azole resistance that lead to an intensified pathogenicity and treatment failure. We aimed to evaluate the virulence factors and molecular mechanisms of azole resistance among C. tropicalis isolated from patients with candidemia. Several virulence factors, including extracellular enzymatic activities, cell surface hydrophobicity (CSH), and biofilm formation, were evaluated. Antifungal susceptibility pattern and expression level of ERG11, UPC2, MDR1, and CDR1 genes of eight (4 fluconazole resistance and 4 fluconazole susceptible) clinical C. tropicalis isolates were assessed. The correlation between the virulence factors and antifungal susceptibility patterns was analyzed. During a 4year study, forty-five C. tropicalis isolates were recovered from candidemia patients. The isolates expressed different frequencies of virulence determinants as follows: coagulase 4 (8.9%), phospholipase 5 (11.1%), proteinase 31 (68.9%), esterase 43 (95.6%), hemolysin 44 (97.8%), biofilm formation 45 (100%) and CSH 45(100%). All the isolates were susceptible to amphotericin B and showed the highest resistance to voriconazole. There was a significant positive correlation between micafungin minimum inhibitory concentrations (MICs) and hemolysin production (rs = 0.316). However, we found a negative correlation between fluconazole MICs and esterase production (rs = -0.383). We observed the high expression of ERG11 and UPC2 genes in fluconazole-resistant C. tropicalis isolates. C. tropicalis isolated from candidemia patients extensively displayed capacities for biofilm formation, hemolysis, esterase activity, and hydrophobicity. In addition, the overexpression of ERG11 and UPC2 genes was considered one of the possible mechanisms of azole resistance.

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM BackgroundLimited knowledge exists on the virulence factors of Candida tropicalis and the mechanisms of azole resistance that lead to an intensified pathogenicity and treatment failure. We aimed to evaluate the virulence factors and molecular mechanisms of azole resistance among C. tropicalis isolated from patients with candidemia.Materials and MethodsSeveral virulence factors, including extracellular enzymatic activities, cell surface hydrophobicity (CSH), and biofilm formation were evaluated. Antifungal susceptibility pattern and expression level of ERG11, UPC2, MDR1, and CDR1 genes of 8 (4 fluconazole resistance and 4 fluconazole susceptible) clinical C. tropicalis isolates were assessed. The correlation between the virulence factors and antifungal susceptibility patterns was analyzed.ResultsDuring a 4-year study, 45 C. tropicalis isolates were recovered from candidemia patients. The isolates expressed different frequencies of virulence determinants as follows: coagulase 4 (8.9%), phospholipase 5 (11.1%), proteinase 31 (68.9%), esterase 43 (95.6%), hemolysin 44 (97.8%), biofilm formation 45 (100%), and CSH 45(100%). All the isolates were susceptible to amphotericin B and showed the highest resistance to voriconazole. There was a significant positive correlation between micafungin minimum inhibitory concentrations (MICs) and hemolysin production (rs = 0.316). However, we found a negative correlation between fluconazole MICs and esterase production (rs = −0.383). We observed the high expression of ERG11 and UPC2 genes in fluconazole-resistant C. tropicalis isolates.ConclusionCandida tropicalis isolated from candidemia patients extensively displayed capacities for biofilm formation, hemolysis, esterase activity, and hydrophobicity. In addition, the overexpression of ERG11 and UPC2 genes was considered one of the possible mechanisms of azole resistance.

ABSTRACTThe multiplicity of mechanisms of resistance to azole antifungal agents has been described. As fluconazole- resistant clinical Candida albicans isolates that constitutively over-express ERG11 have been identified in previous studies, the aim of this study is to investigate this molecular mechanism involved in fluconazole resistance of C. albicans clinical isolates. Fluconazole susceptibility testing was carried out on clinical isolates of Candida spp. obtained from hospitalised children in an Iranian referral children's hospital. A polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique was used to differentiate Candida spp. The resistant C. albicans isolates were subjected to RT-qPCR using primers that identify ERG11 gene expression. Of the 142 Candida spp. isolates studied, C. albicans was the most predominant isolate, occurring in 68.3% (97/142) of the patients. According to the CLSI method, the majority of the C. albicans isolates (91.7%, 89/97), categorised as susceptible (minimum inhibitory concentration [MIC] ≤8 μg/mL), five isolates were considered resistant (MIC ≥64 μg/mL) and three had dose-dependent susceptibility (MIC=8.16–32 μg/mL). The ERG11 gene in the five fluconazole-resistant C. albicans isolates was upregulated 4.15–5.84-fold relative to the ATCC 10231 control strain. In this study, the expression of ERG11 was upregulated in all the fluconazole-resistant C. albicans isolates. There are limited data on the antifungal susceptibility of Candida spp. as well as the molecular mechanism of azole resistance in Iran, especially for isolates causing infections in children. Therefore, the surveillance of antifungal resistance patterns and investigation of other mechanisms of azole resistance in all Candida spp. isolates is recommended.

Cleft lip and palate (CLP) patients are prone to Candida infections (oral thrush) mainly due to poor oral hygiene, repetitive surgeries, and orthodontic procedures. This study was undertaken to evaluate the antifungal efficacy of limonene against clinical Candida isolates from CLP patients. The antifungal efficacy of limonene was studied alone and in combination with fluconazole (FLC) against six standards, twenty nine FLC sensitive, and three FLC resistant clinical strains using broth dilution, checkerboard microdilution, agar disk diffusion, growth curves, and spot assays. This nontoxic monoterpene gave low minimum inhibitory concentration (MIC) values of 300-375 µg/mL and 500-520 µg/mL for FLC susceptible and FLC resistant strains, respectively. It showed synergistic interaction with FLC in all clinical and standard Candida strains (fractional inhibitory concentration (FIC) index ≤0.5). Significant chemosensitization of FLC was observed even against resistant clinical isolates. Complete suppression of fungal growth was observed when using combinations. Negligible toxicity, easy availability, and potent antifungal properties suggest that limonene and FLC combinations in appropriate doses can make excellent antifungal mouthwashes during CLP treatment pre and post surgery. Impending in vivo studies are needed to validate the present data.

Today, antimicrobial resistance is the number one problem worldwide. According to the latest data, it has found that Acinetobacter baumani, Pseudomonas aeruginosa, Klebsiela pneumonia and Enterobacter cloacae are predominant among all isolated resistant pathogens. So, the search of a new antibacterial drug that can deal with antimicrobial resistance is task number one. Aim. The study aimed to investigate theoretical and practical relationship of structure and antibacterial activity of quercetin and rutin against test Gram-negative strains: Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, and clinical resistant strains such as Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Enterobacter cloacae. Materials and methods. The research subjects were quercetin and rutin. The theoretical research was carried out using AutoDockTools 1.5.6; antibacterial effects were evaluated by the well method. Clinical strain of P. aeruginosa, A. baumani, K. pneumonia, E. cloacea were taken from tracheal aspirate and bronchoalveolar lavage. Results. Theoretical studies showed that none of the investigated antimicrobial drugs inhibit all “targets” mechanism of antibacterial action. Rutin revealed high selectivity to DNA-gyrase, dihydrofolate reductase (DHFR), deacetylase, AHS RhI, Diguanylate cyclase, unlike quercetin which revealed low selectivity. Experimental research demonstrated that against P. aeruginosa rutin and quercetin inhibited growth – 17.0 ± 0.4 mm and 18.0 ± 0.4 mm, against P. vulgaris – 14.0 ± 0.5 mm and 16.0 ± 0.5 mm, against E. coli – 16.0 ± 0.5 mm and 20.0 ± 0.4 mm, respectively. Resistant strain of P. aeruginosa, E. cloacea, A. baumani, K. pneumonia were sensitive to the action of rutin – 23.0 ± 0.3 mm, 25.0 ± 0.2 mm, 24.0 ± 0.3 mm, 23.0 ± 0.3 mm, respectively, while to the action of quercetin resistant strain were low sensitive – 12.0 ± 0.6 mm, 14.0 ± 0.5 mm, 12.0 ± 0.6 mm, 12.0 ± 0.6 mm, respectively. Conclusions. Theoretical studies of “standard” antimicrobial drugs used in infectious disease treatment protocols are not highly selective inhibitors of “target” antibacterial mechanisms of gram-negative bacteria, unlike rutin, which turned out to be a highly selective inhibitor. According to the results of the theoretical study, it was found that the potential antibacterial activity of rutin exceeds the effect of quercetin by two times. This pattern is fully confirmed by in vitro studies, where the antibacterial effect of rutin against resistant strains was also two times higher.

Azole and echinocandin resistance mechanisms and genotyping of Candida tropicalis in Japan: cross-boundary dissemination and animal–human transmission of C. tropicalis infection

BackgroundFungal infections are common life-threatening diseases amongst immunodeficient individuals. Invasive fungal disease is commonly treated with an azole antifungal agent, resulting in selection pressure and the emergence of drug resistance. Antifungal resistance is associated with higher mortality rates and treatment failure, making the current clinical management of fungal disease very challenging. Clinical isolates from a variety of fungi have been shown to contain mutations in the MSH2 gene, encoding a component of the DNA mismatch repair pathway. Mutation of MSH2 results in an elevated mutation rate that can increase the opportunity for selectively advantageous mutations to occur, accelerating the development of antifungal resistance.ObjectivesTo characterize the molecular mechanisms causing the microevolutionary emergence of antifungal resistance in msh2 mismatch repair mutants of Cryptococcus neoformans.MethodsThe mechanisms resulting in the emergence of antifungal resistance were investigated using WGS, characterization of deletion mutants and measuring ploidy changes.ResultsThe genomes of resistant strains did not possess mutations in ERG11 or other genes of the ergosterol biosynthesis pathway. Antifungal resistance was due to small contributions from mutations in many genes. MSH2 does not directly affect ploidy changes.ConclusionsThis study provides evidence that resistance to fluconazole can evolve independently of ERG11 mutations. A common microevolutionary route to the emergence of antifungal resistance involves the accumulation of mutations that alter stress signalling, cellular efflux, membrane trafficking, epigenetic modification and aneuploidy. This complex pattern of microevolution highlights the significant challenges posed both to diagnosis and treatment of drug-resistant fungal pathogens.

Mechanisms of azole resistance in Candida albicans clinical isolates from Shanghai, China

In this study, we describe the membrane lipid composition of eight clinical isolates (azole resistant and sensitive strains) of Candida albicans isolated from AIDS/ HIV patients. Interestingly, fluorescence polarization measurements of the clinical isolates displayed enhanced membrane fluidity in fluconazole resistant strains as compared to the sensitive ones. The increase in fluidity was reflected in the change of membrane order, which was considerably decreased (decrease in fluorescence polarization "p" value denotes higher membrane fluidity) in the resistant strains. The ergosterol content in azole susceptible isolates was greater, almost twice as compared to the resistant isolates. However, no significant alteration was observed in phospholipid and fatty acid composition of these isolates. Labeling experiments with fluorescamine dye revealed that the percentage of phosphatidylethanolamine exposed to the membrane's outer leaflet was higher in the resistant strains as compared to the sensitive strains, indicating increased floppase activity of the two major ABC drug efflux pumps, CDR1 and CDR2 possibly due to their overexpression in resistant strains. The results of the present study suggest that changes in the status of membrane lipid phase especially the ergosterol content and increased activity of drug efflux pumps by overexpression ofABC transporters, CDR1 and CDR2 might contribute to fluconazole resistance in C. albicans isolated from AIDS/HIV patients.

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM ObjectiveCandida auris is a multidrug-resistant pathogen that presents a serious global threat to human health. The U.S. Centers for Disease Control and Prevention has classified C. auris as an urgent threat to public health due to its clinical and economic impact and future projections of new infections over the next 10 years. Candida auris infections are difficult to treat since many isolates display high levels of resistance to fluconazole and exhibit variable resistance to amphotericin B and echinocandins. In this study, we performed comparative transcriptomics to understand the molecular mechanisms associated with azole-resistance in C. auris environmental isolates.Material and MethodsTwo sets of environmental isolates including azole-resistant (n = 2) and azole susceptible (n = 1) isolates were used for RNA-Seq analysis. Pair-wise comparisons in edgeR were used for comparing the number of differentially expressed genes (DEGs) between the azole susceptible and resistant isolates. GO term enrichment analysis was performed using the ‘enrichGO’ function from the cluster Profiler package. Only GO categories with a q-value <0.05 were considered significant.ResultsOur data show significant enrichment of ergosterol biosynthesis genes, drug transport, MAPK pathway as well as chromatin remodeling genes in azole-resistant strains compared to susceptible isolates. A total of 468 and 564 differentially expressed genes were identified in two azole-resistant isolates compared with the susceptible strain. A large number of multidrug transporter genes (CDR1, MDR1, HGT2, HGT7, HGT13, HGT17, and NGT1) were differentially expressed between the two sets of strains. Interestingly, the overexpression of ERG11 (azole target gene), and CDR1 (drug transporter) genes was observed in resistant isolates as compared with susceptible strain. Furthermore, resistant strain has two copies of ERG11 while susceptible isolate has single copy of ERG11. Notably, 8/21 genes involved in the ergosterol biosynthesis pathway were found to be induced in azole resistant isolates. These include HMG1, ERG1, ERG2, ERG3, ERG6, ERG10, ERG13, and ERG25. Furthermore, other multidrug transporters MDR1 and SNQ2 responsible for azole resistance in other Candida species like C. glabrata also showed significant expression changes between the two sets of isolates. Furthermore, HGT7 (glucose transporter) and NGT1, (N-acetyl glucosamine transporter) genes associated with azole and polyene resistance were found to be upregulated in the resistant isolate as compared with susceptible strain. Additionally, a Glycophosphatidylinositol (GPI)-anchored protein unique for C. auris, PGA7 was found to be overexpressed in resistant isolate. Importantly, we also identified several secreted aspartic proteases (SAP3, SAP5, SAP8, and SAP9) to be downregulated between the two sets.ConclusionThe present study identifies several gene families that are differentially expressed in azole resistant vs susceptible C. auris strains. These findings suggest that azole-resistance in C. auris environmental isolates is influenced by changes in cell wall, lipid, and ergosterol biosynthesis. Overall, these data provide a framework for the mechanistic understanding of azole resistance mechanisms in C. auris environmental isolates.