Comparative Evaluations of the Pathogenesis of Candida auris Phenotypes and Candida albicans Using Clinically Relevant Murine Models of Infections

Lansoprazole interferes with fungal respiration and acts synergistically with amphotericin B against multidrug-resistant Candida auris

Candida auris has emerged as a problematic fungal pathogen associated with high morbidity and mortality. Amphotericin B (AmB) is the most effective antifungal used to treat invasive fungal candidiasis, with resistance rarely observed among clinical isolates. However, C. auris possesses extraordinary resistant profiles against all available antifungal drugs, including AmB. In our pursuit of potential solutions, we screened a panel of 727 FDA-approved drugs. We identified the proton pump inhibitor lansoprazole (LNP) as a potent enhancer of AmB's activity against C. auris. LNP also potentiates the antifungal activity of AmB against other medically important species of Candida and Cryptococcus. Our investigations into the mechanism of action unveiled that LNP metabolite(s) interact with a crucial target in the mitochondrial respiratory chain (complex III, known as cytochrome bc1). This interaction increases oxidative stress within fungal cells. Our results demonstrated the critical role of an active respiratory function in the antifungal activity of LNP. Most importantly, LNP restored the efficacy of AmB in an immunocompromised mouse model, resulting in a 1.7-log (∼98%) CFU reduction in the burden of C. auris in the kidneys. Our findings strongly advocate for a comprehensive evaluation of LNP as a cytochrome bc1 inhibitor for combating drug-resistant C. auris infections.

Uniqueness of Candida auris cell wall in morphogenesis, virulence, resistance, and immune evasion

Candida auris has drawn global attention due to its alarming multidrug resistance and the emergence of pan resistant strains. C. auris poses a significant risk in nosocomial candidemia especially among immunocompromised patients. C. auris showed unique virulence characteristics associated with cell wall including cell polymorphism, adaptation, endurance on inanimate surfaces, tolerance to external conditions, and immune evasion. Notably, it possesses a distinctive cell wall composition, with an outer mannan layer shielding the inner 1,3-β glucan from immune recognition, thereby enabling immune evasion and drug resistance. This review aimed to comprehend the association between unique characteristics of C. auris's cell wall and virulence, resistance mechanisms, and immune evasion. This is particularly relevant since the fungal cell wall has no human homology, providing a potential therapeutic target. Understanding the complex interactions between the cell wall and the host immune system is essential for devising effective treatment strategies, such as the use of repurposed medications, novel therapeutic agents, and immunotherapy like monoclonal antibodies. This therapeutic targeting strategy of C. auris holds promise for effective eradication of this resilient pathogen.

Intradermal infection and dissemination of Candida auris in immunocompetent and immunocompromised mouse models

Candida auris, an emerging fungal pathogen, predominately colonizes human skin leading to serious invasive infections in humans. Though it is assumed that skin colonization can lead to invasive infection, dissemination potential of C. auris from skin to internal organs is still unknown. In this study, immunocompetent and immunocompromised mouse models of intradermal skin infection were used to compare the dissemination potential of C. auris to internal organs. Our results suggest that C. auris persists in the skin tissue of both immunocompetent and immunocompromised infected mice even at 30 days post-infection. Furthermore, C. auris can readily disseminate from skin tissue to internal organs such as the spleen and kidney as early as 24 h post-infection and was detected until 30 days post-infection. Taken together, our findings for the first time indicate that murine skin intradermally infected with C. auris can readily disseminate to internal organs and cause invasive infections.

IMPORTANCE

Candida auris is a multi-drug-resistant emerging fungal pathogen colonizes the human skin and causes life-threatening infections. However, whether C. auris can disseminate from the skin to internal organs is unclear. Understanding the dissemination potential of C. auris in both immunocompetent and immunocompromised hosts is necessary to monitor susceptible individuals and to develop novel approaches to prevent and treat this emerging fungal pathogen. Using mouse models of intradermal C. auris skin infection, our findings report a novel observation that mice skin intradermally infected with C. auris can readily disseminate to internal organs leading to systemic disease. These findings help explain the colonization, persistence, and dissemination potential of C. auris in immunocompetent and immunocompromised hosts and reveal that skin infection is a potential source of invasive infection.

Innate immune response to Candida auris

Candida auris, a newly emergent fungal species, has been spreading in health care systems and causing life-threatening infections. Intact innate immunity is essential for protection against many invasive fungal infections, including candidiasis. Here, we highlight recent studies exploring immune interactions with C. auris, including investigations using animal models and ex vivo immune cells. We summarize innate immune studies comparing C. auris and the common fungal pathogen Candida albicans. We also discuss how structures of the C. auris cell wall influence immune recognition, the role of soluble host factors in immune recognition, and areas of future study.

Candida auris Updates: Outbreak Evaluation through Molecular Assays and Antifungal Stewardship-A Narrative Review

Candida auris was reported by the WHO as second to Cryptococcus neoformans, in the list of nineteen fungal priority pathogens, along with two species with a new nomenclature, Nakaseomyces glabrata (Candida glabrata) and Pichia kudriavzevii (Candida krusei). This novel classification was based on antifungal resistance, the number of deaths, evidence-based treatment, access to diagnostics, annual incidence, and complications and sequelae. We assessed which molecular assays have been used to diagnose Candida auris outbreaks in the last five years. Using "Candida auris; outbreak; molecular detection" as keywords, our search in PubMed revealed 32 results, from which we selected 23 original papers published in 2019-2024. The analyzed studies revealed that the detection methods were very different: from the VITEK® 2 System to MALDI TOF (Matrix-Assisted Laser Desorption Ionization-Time of Flight), NGS (Next-Generation Sequencing), WGS (Whole Genome Sequencing), and commercially available real-time PCR (Polymerase Chain Reaction) assays. Moreover, we identified studies that detected antifungal resistance genes (e.g., FKS for echinocandins and ERG11 for azoles). The analyzed outbreaks were from all continents, which confirms the capability of this yeast to spread between humans and to contaminate the environment. It is important that real-time PCR assays were developed for accurate and affordable detection by all laboratories, including the detection of antifungal resistance genes. This will allow the fast and efficient implementation of stewardship programs in hospitals.

A correlative study of the genomic underpinning of virulence traits and drug tolerance of Candida auris

Candida auris is an opportunistic fungal pathogen with high mortality rates which presents a clear threat to public health. The risk of C. auris infection is high because it can colonize the body, resist antifungal treatment, and evade the immune system. The genetic mechanisms for these traits are not well known. Identifying them could lead to new targets for new treatments. To this end, we present an analysis of the genetics and gene expression patterns of C. auris carbon metabolism, drug resistance, and macrophage interaction. We chose to study two C. auris isolates simultaneously, one drug sensitive (B11220 from Clade II) and one drug resistant (B11221 from Clade III). Comparing the genomes, we confirm the previously reported finding that B11220 was missing a 12.8 kb region on chromosome VI. This region contains a gene cluster encoding proteins related to alternative sugar utilization. We show that B11221, which has the gene cluster, readily assimilates and utilizes D-galactose and L-rhamnose as compared to B11220, which harbors the deletion. B11221 exhibits increased adherence and drug resistance compared to B11220 when grown in these sugars. Transcriptomic analysis of both isolates grown on glucose or galactose showed that the gene cluster was upregulated when grown on D-galactose. These findings reinforce growing evidence of a link between metabolism and drug tolerance. B11221 resists phagocytosis by macrophages and exhibits decreased β-1,3-glucan exposure, a key determinant that allows Candida to evade the host immune system, as compared to B11220. In a transcriptomic analysis of both isolates co-cultured with macrophages, we find upregulation of genes associated with transport and transcription factors in B11221. Our studies show a positive correlation between membrane composition and immune evasion, alternate sugar utilization, and drug tolerance in C. auris.

Lower (1,3)-beta-d-glucan sensitivity and in vitro levels in Candida auris and Candida parapsilosis strains

OBJECTIVES

The serum (1,3)-beta-d-glucan (BDG) assay gives quicker results and has higher sensitivity than blood cultures, therefore it is advised for early diagnosis of invasive candidemia and/or discontinuation of empirical therapy. Its sensitivity may depend on different factors. The aim of our study was to analyse the in vitro and in vivo BDG levels in clinical isolates of three species of Candida responsible for candidemia.

METHODS

C. albicans, C. parapsilosis, and C. auris strains were collected from blood cultures of patients who had a concurrent (-1 to +3 days) serum BDG test (Fungitell assay). Supernatants of all strains were tested in quadruplicate for BDG levels.

RESULTS

Twenty-two C. auris, 14 C. albicans, and ten C. parapsilosis strains were included. The median BDG levels in supernatants were 463 pg/mL (interquartile range [IQR] 379-648) for C. auris, 1080 pg/mL (IQR 830-1276) for C. albicans, and 755 pg/mL (IQR 511-930) for C. parapsilosis, with the significant difference among the species (p < 0.0001). Median serum BDG levels (IQR) were significantly lower in case C. auris and C. parapsilosis vs. C. albicans (p < 0.0001), respectively, 50 pg/mL (IQR 15-161) and 57 pg/mL (IQR 18-332), vs. 372 pg/mL (IQR 102-520). Sensitivity of serum BDG was 39% (95% confidence interval [CI], 18-64) in case of C. auris, 30% (95% CI, 8-65) C. parapsilosis and 78% (95% CI, 49-94) C. albicans candidemia.

DISCUSSION

In our centre C. auris and C. parapsilosis strains have lower BDG content as compared with C. albicans, with a potential impact on serum BDG performance for the diagnosis of candidemia.

Functional Redundancy in Candida auris Cell Surface Adhesins Crucial for Cell-Cell Interaction and Aggregation

Candida auris is an emerging nosocomial fungal pathogen associated with life-threatening invasive disease due to its persistent colonization, high level of transmissibility and multi-drug resistance. Aggregative and non-aggregative growth phenotypes for C. auris strains with different biofilm forming abilities, drug susceptibilities and virulence characteristics have been described. Using comprehensive transcriptional analysis we identified key cell surface adhesins that were highly upregulated in the aggregative phenotype during in vitro and in vivo grown biofilms using a mouse model of catheter infection. Phenotypic and functional evaluations of generated null mutants demonstrated crucial roles for the adhesins Als5 and Scf1 in mediating cell-cell adherence, coaggregation and biofilm formation. While individual mutants were largely non-aggregative, in combination cells were able to co-adhere and aggregate, as directly demonstrated by measuring cell adhesion forces using single-cell atomic force spectroscopy. This co-adherence indicates their role as complementary adhesins, which despite their limited similarity, may function redundantly to promote cell-cell interaction and biofilm formation. Functional diversity of cell wall proteins may be a form of regulation that provides the aggregative phenotype of C. auris with flexibility and rapid adaptation to the environment, potentially impacting persistence and virulence.

Functional Redundancy in Candida auris Cell Surface Adhesins Crucial for Cell-Cell Interaction and Aggregation

Candida auris is an emerging nosocomial fungal pathogen associated with life-threatening invasive disease due to its persistent colonization, high level of transmissibility and multi-drug resistance. Aggregative and non-aggregative growth phenotypes for C. auris strains with different biofilm forming abilities, drug susceptibilities and virulence characteristics have been described. Using comprehensive transcriptional analysis we identified key cell surface adhesins that were highly upregulated in the aggregative phenotype during in vitro and in vivo grown biofilms using a mouse model of catheter infection. Phenotypic and functional evaluations of generated null mutants demonstrated crucial roles for the adhesins Als5 and Scf1 in mediating cell-cell adherence, coaggregation and biofilm formation. While individual mutants were largely non-aggregative, in combination cells were able to co-adhere and aggregate, as directly demonstrated by measuring cell adhesion forces using single-cell atomic force spectroscopy. This co-adherence indicates their role as complementary adhesins, which despite their limited similarity, may function redundantly to promote cell-cell interaction and biofilm formation. Functional diversity of cell wall proteins may be a form of regulation that provides the aggregative phenotype of C. auris with flexibility and rapid adaptation to the environment, potentially impacting persistence and virulence.

A novel zinc-chelating compound has antifungal activity against a wide range of Candida species, including multidrug-resistant Candida auris

Objectives

In recent years, the incidence of invasive fungal infections has increased, resulting in considerable morbidity and mortality, particularly among immunocompromised individuals. Potential challenges in treating these infections with the few existing antifungal agents highlight the urgency of developing new ones. Here, we evaluated six alkyl polyamine compounds (APCs), not previously reported as antifungal drugs to our knowledge, that could deprive fungi of essential transition metals.

Methods

The APC with confirmed antifungal activity against Candida spp. was analysed by using transcriptomics, followed by metal-addition experiments, mass spectrometric analyses and intracellular zinc quantification with a fluorescent probe.

Results

A cyclic APC with three pyridylmethyl groups, APC6, had high antifungal activity against a wide range of Candida species, including MDR Candida auris. We conclusively demonstrated that APC6 was able to capture zinc within fungal cells. APC6 not only exhibited activity against C. auris as a single agent but also enhanced the efficacy of an azole antifungal agent, voriconazole, in vitro and in vivo. APC6 disrupted the biofilms formed by Candida species.

Conclusions

This zinc-chelating compound has potential as an antifungal agent, and the control of zinc levels in Candida species could be a powerful approach to treating drug-resistant candidiasis.

Differential skin immune responses in mice intradermally infected with Candida auris and Candida albicans

IMPORTANCE

Candida auris is a globally emerging fungal pathogen that transmits among individuals in hospitals and nursing home residents. Unlike other Candida species, C. auris predominantly colonizes and persists in skin tissue, resulting in outbreaks of nosocomial infections. Understanding the factors that regulate C. auris skin colonization is critical to develop novel preventive and therapeutic approaches against this emerging pathogen. We established a model of intradermal C. auris inoculation in mice and found that mice infected with C. auris elicit less potent innate and adaptive immune responses in the infected skin compared to C. albicans. These findings help explain the clinical observation of persistent C. auris colonization in skin tissue.

Mechanisms of pathogenicity for the emerging fungus Candida auris

Candida auris recently emerged as an urgent public health threat, causing outbreaks of invasive infections in healthcare settings throughout the world. This fungal pathogen persists on the skin of patients and on abiotic surfaces despite antiseptic and decolonization attempts. The heightened capacity for skin colonization and environmental persistence promotes rapid nosocomial spread. Following skin colonization, C. auris can gain entrance to the bloodstream and deeper tissues, often through a wound or an inserted medical device, such as a catheter. C. auris possesses a variety of virulence traits, including the capacity for biofilm formation, production of adhesins and proteases, and evasion of innate immune responses. In this review, we highlight the interactions of C. auris with the host, emphasizing the intersection of laboratory studies and clinical observations.

Identification of Candida auris by PCR and assessment of biofilm formation by crystal violet assay

INTRODUCTION

Candida auris is a notorious pathogen capable of forming biofilms on devices as well as host tissues, often culminating in infections. We evaluated characteristics of infections and the methods to diagnose C. auris over a period of three years in a tertiary care hospital.

METHODS

Patients admitted between 2018 and 2020, who had candidemia due to C. auris were included in the study. Identification was performed using HiCrome™ Candida Differential Agar, Vitek 2 (BioMérieux, Inc., Marcy-l'Etoile, France) and MALDI-TOF, Vitek-MS. Identification was confirmed by detection of rDNA region covering part of 5.8S, entire of ITS2, and part of 28S by polymerase chain reaction (PCR). Biofilm formation was assessed by crystal violet staining.

RESULTS

Presence of central line and broad spectrum antimicrobials were noted in all patients whereas total parenteral nutrition was given in 82.1% of these patients. Identification by Vitek2 v8.1 correlated with MALDI-TOF MS. PCR products of length 163 ​bp were obtained in all isolates as visualized by agarose gel electrophoresis. The biofilm quantity measured as A560 of the twenty-eight C. auris isolates ranged from 0.16 to 0.80 compared to C. albicans.

CONCLUSIONS

C. auris can be identified by PCR targeting specific rDNA region. Biofilm formation and quantification can be achieved by growing C. auris isolates in Mueller-Hinton broth over a duration of 48 ​h.

A Candida auris-specific adhesin, Scf1, governs surface association, colonization, and virulence

Candida auris is an emerging fungal pathogen responsible for health care-associated outbreaks that arise from persistent surface and skin colonization. We characterized the arsenal of adhesins used by C. auris and discovered an uncharacterized adhesin, Surface Colonization Factor (Scf1), and a conserved adhesin, Iff4109, that are essential for the colonization of inert surfaces and mammalian hosts. SCF1 is apparently specific to C. auris, and its expression mediates adhesion to inert and biological surfaces across isolates from all five clades. Unlike canonical fungal adhesins, which function through hydrophobic interactions, Scf1 relies on exposed cationic residues for surface association. SCF1 is required for C. auris biofilm formation, skin colonization, virulence in systemic infection, and colonization of inserted medical devices.

Beyond Ergosterol: Strategies for Combatting Antifungal Resistance in Aspergillus fumigatus and Candida auris

Aspergillus fumigatus and Candida auris are historically problematic fungal pathogens responsible for systemic infections and high mortality rates, especially in immunocompromised populations. The three antifungal classes that comprise our present day armamentarium have facilitated efficacious treatment of these fungal infections in past decades, but their potency has steadily declined over the years as resistance to these compounds has accumulated. Importantly, pan-resistant strains of Candida auris have been observed in clinical settings, leaving affected patients with no treatment options and a death sentence. Many compounds in the ongoing antifungal drug discovery pipeline, similar to those within our aforementioned trinity, are predicated on the binding or inhibition of ergosterol. Recurring accounts of resistance to antifungals targeting this pathway suggest optimization of ergosterol-dependent antifungals is likely not the best solution for the long-term. This review aims to present several natural products with novel or underexplored biological targets, as well as similarly underutilized drug discovery strategies to inspire future biological investigations and medicinal chemistry campaigns.

Candida auris biofilm: a review on model to mechanism conservation

INTRODUCTION

Candida auris is included in the fungal infection category 'critical' by WHO because of associated high drug tolerance and spread at an alarming rate which if remains untouched may result in serious outbreaks. Since its discovery in 2009, several assiduous efforts by mycologists across the world have deciphered its biology including growth physiology, drug tolerance, biofilm formation, etc. The differential response of various strains from different clades poses a hurdle in drawing a final conclusion.

AREAS COVERED

This review provides brief insights into the understanding of C. auris biofilm. It includes information on various models developed to understand the biofilms and conservation of different signaling pathways. Significant development has been made in the recent past with the generation of relevant in vivo and ex vivo models. The role of signaling pathways in the development of biofilm is largely unknown.

EXPERT OPINION

The selection of an appropriate model system is a must for the accuracy and reproducibility of results. The conservation of major signaling pathways in C. auris with respect to C. albicans and S. cerevisiae highlights that initial inputs acquired from orthologs will be valuable in getting insights into the mechanism of biofilm formation and associated pathogenesis.

Intestinal colonization with Candida auris and mucosal immune response in mice treated with cefoperazone oral antibiotic

Candida auris, an emerging multi-drug resistant fungal pathogen, causes invasive infections in humans. The factors regulating the colonization of C. auris in host niches are not well understood. In this study, we examined the effect of antibiotic-induced gut dysbiosis on C. auris intestinal colonization, dissemination, microbiome composition and the mucosal immune response. Our results indicate that mice treated with cefoperazone alone had a significant increase in C. auris intestinal colonization compared to untreated control groups. A significant increase in the dissemination of C. auris from the intestine to internal organs was observed in antibiotic-treated immunosuppressed mice. Intestinal colonization of C. auris alters the microbiome composition of antibiotic-treated mice. Relative abundance of firmicutes members mainly Clostridiales and Paenibacillus were considerably increased in the cefoperazone-treated mice infected with C. auris compared to cefoperazone-treated uninfected mice. Next, we examined the mucosal immune response of C. auris infected mice and compared the results with Candida albicans infection. The number of CD11b+ CX3CR1+ macrophages was significantly decreased in the intestine of C. auris infected mice when compared to C. albicans infection. On the other hand, both C. auris and C. albicans infected mice had a comparable increase of the number of Th17 and Th22 cells in the intestine. A significant increase in Candida-specific IgA was observed in the serum of C. auris but not in the C. albicans infected mice. Taken together, treatment with broad-spectrum antibiotic increased the colonization and dissemination of C. auris from the intestine. Furthermore, findings from this study for the first time revealed the microbiome composition, innate and adaptive cellular immune response to intestinal infection with C. auris.

Down-regulation of microRNA-155 suppressed Candida albicans induced acute lung injury by activating SOCS1 and inhibiting inflammation response

Acute lung injury caused by Candida albicans could result in high mortality and morbidity. MicroRNA-155 (miR-155) and suppressor of cytokine signaling 1 (SOCS1) have been believed to play a key in the regulation of inflammatory response. Whether miR-155/SOCS1 axis could regulate the acute lung injury caused by C. albicans has not been reported. The acute lung injury animal model was established with acute infection of C. albicans. miR-155 inhibitor, miR-155 mimic, and sh-SOCS1 were constructed. The binding site between miR-155 and SOCS1 was identified with dual luciferase reporter assay. Knockdown of miR-155 markedly inhibited the germ tube formation of C. albicans. Knockdown of miR-155 significantly up-regulated the expression of SOCS1, and the binding site between miR-155 and SOCS1 was identified. Knockdown of miR-155 improved the acute lung injury, suppressed inflammatory factors and fungus loading through SOCS1. Knockdown of SOCS1 greatly reversed the influence of miR-155 inhibitor on the cell apoptosis in vitro. The improvement of acute lung injury caused by C. albicans, suppression of inflammatory response and C. albicans infection, and inhibitor of cell apoptosis were achieved by knocking down miR-155 through SOCS1. This research might provide a new thought for the prevention and treatment of acute lung injury caused by C. albicans through targeting miR-155/SOCS1 axis.

A Human Ex Vivo Skin Model to Study Candida auris Biofilms

Candida auris can persist for long periods on hospital surfaces and on the skin. C. auris has the ability to form drug-resistant biofilms, which can substantially impact on patient outcome. In comparison to Candida albicans, C. auris has a lower capacity to form biofilms in in vitro models and a higher capacity when tested on animal skin models. Intraspecies variation is shown to exist, with some clinical isolates having greater biofilm capabilities than others. There is a need for models that closely mimic the real niches where infection occurs on human patients. This protocol describes, in detail, a human skin model to study C. auris biofilm formation using catheterized and non-catheterized skin.

Colonization by Candida auris in critically ill patients: role of cutaneous and rectal localization during an outbreak

BACKGOROUND

Candida auris infections were reported worldwide since the pathogen was isolated in 2009. In a hospital setting of a C. auris epidemic, we analyzed incidence of cutaneous and intestinal colonization, and connection with infections by the organism.

METHODS

This was a retrospective study in intensive care units at a 1200-bed Italian hospital. The incidence of cutaneous positive swabs, and cutaneous carriers, for C. auris was compared to that of rectal positive swabs, and intestinal carriers, and both were correlated to C. auris infections.

FINDINGS

A total of 399 patients were included. Seventy-seven patients were infected by C. auris. Ratio of C. auris positive skin swabs from screening in ICUs was 24%. The ratio obtained from infected patients and intestinal C. auris carriers was 49.1%, likewise rectal swabs from similar cohort of patients (P = 0.373). 39.7% and 5.5% of this cohort was colonized only in skin and in rectum, respectively, while 54.8% was colonized in both sites. 12.3% and 83.6% of skin swabs was, respectively, always positive and variable over time in single subject, while 31.5% and 41.1% of rectal swabs were always positive and variable (P = 0.000). Intestinal colonization was associated with increased risk for C. auris urinary infections (P = 0.006).

CONCLUSIONS

C. auris intestinal carriers were fewer than cutaneous carriers, but more continously colonized. Rectal and skin swabs can be good tools for surveillance, respectively, of colonization and of hygiene measures effectiveness. Urinary tract infections by C. auris appeared increasing with gastrointestinal presence of the yeast.

Comparison of β-D-Glucan levels between Candida auris and other Candida species at the time of candidaemia: a retrospective study

OBJECTIVES

To compare serum β-D-glucan (BDG) levels in candidaemia with different Candida species, especially C. auris.

METHODS

Aga Khan University clinical laboratory database was retrospectively reviewed from January 2015 to December 2019. Blood culture positive cases with any Candida species and concomitant BDG level were included.

RESULTS

Among the 192 cases included in our study, 48 were C. albicans, 54 C. auris, eight C. glabrata, 32 C. parapsilosis, 43 C. tropicalis and seven other Candida species. The level of BDG was significantly lower in C. auris (median 62.43, interquartile range (IQR) 12.80-182.94 pg/mL) compared to C. albicans (median 266.83, IQR 66.29-523.43 pg/mL) and C. tropicalis (median 324.41, IQR 105.20-523.44 pg/mL). The sensitivity of serum BDG was significantly lower for C. auris (43.75%, 95% CI 29.5-58.8%) than C. tropicalis (79.07%, 95% CI 64.0-90.0%).

DISCUSSION

Serum BDG has lower sensitivity in patients with suspected C. auris candidaemia in our setting. Considering that C. auris has higher morbidity and mortality than other species, a more sensitive test is required.

Therapeutic implications of C. albicans-S. aureus mixed biofilm in a murine subcutaneous catheter model of polymicrobial infection

Biofilm-associated polymicrobial infections tend to be challenging to treat. Candida albicans and Staphylococcus aureus are leading pathogens due to their ability to form biofilms on medical devices. However, the therapeutic implications of their interactions in a host is largely unexplored. In this study, we used a mouse subcutaneous catheter model for in vivo-grown polymicrobial biofilms to validate our in vitro findings on C. albicans-mediated enhanced S. aureus tolerance to vancomycin in vivo. Comparative assessment of S. aureus recovery from catheters with single- or mixed-species infection demonstrated failure of vancomycin against S. aureus in mice with co-infected catheters. To provide some mechanistic insights, RNA-seq analysis was performed on catheter biofilms to delineate transcriptional modulations during polymicrobial infections. C. albicans induced the activation of the S. aureus biofilm formation network via down-regulation of the lrg operon, repressor of autolysis, and up-regulation of the ica operon and production of polysaccharide intercellular adhesin (PIA), indicating an increase in eDNA production, and extracellular polysaccharide matrix, respectively. Interestingly, virulence factors important for disseminated infections, and superantigen-like proteins were down-regulated during mixed-species infection, whereas capsular polysaccharide genes were up-regulated, signifying a strategy favoring survival, persistence and host immune evasion. In vitro follow-up experiments using DNA enzymatic digestion, lrg operon mutant strains, and confocal scanning microscopy confirmed the role of C. albicans-mediated enhanced eDNA production in mixed-biofilms on S. aureus tolerance to vancomycin. Combined, these findings provide mechanistic insights into the therapeutic implications of interspecies interactions, underscoring the need for novel strategies to overcome limitations of current therapies.