Role of Microbiota in the Skin Colonization of Candida auris

A comprehensive analysis of the effect of quorum-sensing molecule 3-oxo-C12-homoserine lactone on Candida auris and Candida albicans

Candida auris occupies similar niches in various infections as Pseudomonas aeruginosa; however, the details of their interspecies communication remain largely unknown. To gain deeper insights into this relationship, phenotypic and transcriptomic analyses were conducted in the presence of the primary P. aeruginosa quorum-sensing molecule, N-(3-oxododecanoyl)-l-homoserine lactone (HSL), against C. auris, with the results compared to those of C. albicans. Our findings indicate that HSL-induced effects are not specific to C. albicans; additionally, several characteristics are present in C. auris but not in C. albicans following HSL exposure. Significant HSL-induced reduction was observed in growth and adhesion of C. auris cells in time -and concentration-dependent way (p < 0.01-0.001). Moreover, HSL reduced intracellular iron and zinc levels (p < 0.05-0.001); furthermore, it modulated C. auris metabolism toward beta-oxidation, which may be associated with the observed reduction in in vivo virulence at lower HSL concentrations compared with C. albicans. RNA-sequencing transcriptome analysis of C. auris revealed 67 and 306 upregulated genes, as well as 111 and 168 downregulated genes, in response to 100 and 200-μM HSL, respectively. We identified 45 overlapping upregulated and 25 overlapping downregulated genes between the two HSL concentrations. Similar to other Candida-derived C12 compounds (e.g., farnesol), HSL reduces several C. auris survival strategies, which may significantly influence the nature of P. aeruginosa-C. auris co-habitation. In conclusion, the obtained findings on C. auris do not provide clear evidence that HSL mediated effects have any favourable consequences in terms of P. aeruginosa-C. auris co-colonisation and/or co-infections.

Clustered cases of Candida auris colonization: Roles of the infection prevention and control department and the mycology laboratory in controlling transmission

Candida auris is an emerging yeast that is responsible for outbreaks via nosocomial transmission. This study describes two cases of C. auris colonization, with confirmed interhospital transmission in the absence of travel history for the index case, although multiple risk factors were present. The role of the infection prevention and control department is essential in implementing barrier measures to limit yeast transmission, whereas the mycology laboratory plays a crucial role in the rapid and effective detection of potential contact cases, as well as environmental contamination.

Candida albicans Horizontal Transmission in COVID-19 Patients Hospitalized in Intensive Care Unit

BACKGROUND

Invasive candidiasis is a predominant mycosis in hospitalized patients, and Candida albicans is the species most often responsible for this infection. Most candidiasis cases originate from endogenous mycobiota; therefore, Candida strains can easily be transferred among hospital patients and personnel. The aim of this study was to assess the possible horizontal transmission of C. albicans in patients with severe COVID-19 infection requiring hospitalization in the intensive care unit.

METHODS

In total, 59 C. albicans strains from 36 patients were collected from blood and lower-respiratory samples. The strains were genotyped using the RAPD method with the OPA-18 primer (5'-AGCTGACCGT-3'). Antifungal susceptibility testing was performed for amphotericin B (AMB), fluconazole (FCZ), voriconazole (VCZ), and anidulafungin (ANF) using the EUCAST method.

RESULTS

C. albicans strains were separated into 13 different groups according to their RAPD pattern. Two predominant clonal clusters of 17 strains isolated from 12 patients and 12 strains from 7 patients were identified, followed by clusters with 6, 4, and 8 strains isolated from 5, 4, and 3 patients, respectively. C. albicans strains were sensitive to AMB, FCZ, VCZ, and ANF, and antifungal susceptibility profiles were similar in all genetic clusters.

CONCLUSIONS

Our study indicates that C. albicans strains can spread horizontally. The routes of transmission for strains in the ward have not been explained due to there being insufficient data. The transmission could have been caused by the unintentional spread of pathogens by medical personnel.

Characterization and Differentiation of Candida auris on Dixon's Agar Using Raman Spectroscopy

Candida auris, an emerging multidrug-resistant fungal pathogen, poses significant challenges in healthcare settings due to its high misidentification rate and resilience to treatments. Despite advancements in diagnostic tools, a gap remains in rapid, cost-effective identification methods that can differentiate C. auris from other Candida species, particularly on non-standard culture media. We used Raman spectroscopy to characterize C. auris grown on modified Dixon's agar (mDixon) and differentiated it from Candida albicans and Candida parapsilosis. Key Raman spectral markers at 1171 cm-1 and 1452 cm-1, linked to mannan and β-glucan composition, differentiated C. auris into two subgroups, A and B. Despite the spectral similarities of groups A and B with C. albicans and C. parapsilosis, respectively, all Candida species were distinguishable through principal component analysis (PCA). Additionally, this study is the first to demonstrate the distinct spectral signature of mDixon agar, achieved through spatially offset Raman spectroscopy (SORS), which enables accurate discrimination between the culture medium and fungal samples. The observed inter-individual variability within C. auris, coupled with the spectral overlap between C. auris subgroups and other Candida species, highlights a major challenge in differentiating closely related fungi due to their similar molecular composition. Enhancements in spectral resolution and further fluorescence minimization from the culture medium are needed to reliably detect the subtle biochemical differences within these species. Despite these challenges, the results underscore the potential of Raman spectroscopy as a real-time, non-destructive, and complementary tool for fungal pathogen identification.

Candida auris: A focused review for emergency clinicians

INTRODUCTION

Candida auris is an emerging pathogen and human health threat. However, diagnosis and treatment of fungal infection due to C. auris are challenging.

OBJECTIVE

This narrative review provides a focused overview of C. auris for the emergency clinician.

DISCUSSION

C. auris was first identified in 2009 and is currently present on all continents except Antarctica. C. auris possesses multiple genetic factors resulting in antimicrobial resistance, increased virulence and survival within the host, and environmental adaptation. It is readily transmitted from person to person and from the environment to a person, resulting in colonization. Infection may develop days to months following colonization, most commonly in those with immunocompromised state, significant comorbidities or other underlying conditions, healthcare exposure, and recent antimicrobial therapy. Candidemia, device infection (e.g., central venous catheter), soft tissue or wound infection, burn infection, osteomyelitis, myocarditis, meningitis, and urinary tract infection have been associated with C. auris. Samples should be obtained from the suspected site of infection for microbiological culture. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with reference databases to differentiate C. auris from other species is optimal for diagnosis, though other molecular testing methods are available. Treatment is challenging due to antifungal resistance, with over 90% resistant to fluconazole. Echinocandins are most commonly used as the first line therapy. Prevention of colonization and infection are vital and include screening in high-risk populations and strict adherence to infection prevention practices with contact precautions and hand hygiene, as well as appropriate decontamination of patient areas.

CONCLUSION

An understanding of C. auris can assist emergency clinicians in the care of infected or colonized patients.

Assessment of LAMPAuris for Rapid Detection of Candida auris in Clinical Specimens

Candida auris is a pathogenic yeast frequently exhibiting multidrug resistance and thus warrants special attention. The prompt detection and proper identification of this organism are needed to prevent its spread in healthcare facilities. The authors of this paper had previously developed LAMPAuris, a loop-mediated isothermal amplification assay, for the specific detection of C. auris. LAMPAuris is evaluated in this report for its ability to identify C. auris from five clades and to detect it from clinical specimens. A total of 103 skin swab samples were tested in comparison with a culture-based method and C. auris-specific SYBR green qPCR. The results show that the LAMPAuris assay had specificities ranging from 97 to 100% and sensitivities ranging from 66 to 86%. The lower sensitivity could be attributed to DNA degradation caused by the prolonged storage of the samples. In conclusion, LAMPAuris proved to be a rapid and reliable method for identifying C. auris and for detecting it in clinical specimens. Fresh specimens should ensure better yield and higher sensitivities.

Navigating the fungal battlefield: cysteine-rich antifungal proteins and peptides from Eurotiales

Fungi are ubiquitous in the environment and play a key role in the decomposition and recycling of nutrients. On the one hand, their special properties are a great asset for the agricultural and industrial sector, as they are used as source of nutrients, producers of enzymes, pigments, flavorings, and biocontrol agents, and in food processing, bio-remediation and plant growth promotion. On the other hand, they pose a serious challenge to our lives and the environment, as they are responsible for fungal infections in plants, animals and humans. Although host immunity opposes invading pathogens, certain factors favor the manifestation of fungal diseases. The prevalence of fungal infections is on the rise, and there is an alarming increase in the resistance of fungal pathogens to approved drugs. The limited number of antimycotics, the obstacles encountered in the development of new drugs due to the poor tolerability of antifungal agents in patients, the limited number of unique antifungal targets, and the low species specificity contribute to the gradual depletion of the antifungal pipeline and newly discovered antifungal drugs are rare. Promising candidates as next-generation therapeutics are antimicrobial proteins and peptides (AMPs) produced by numerous prokaryotic and eukaryotic organisms belonging to all kingdom classes. Importantly, filamentous fungi from the order Eurotiales have been shown to be a rich source of AMPs with specific antifungal activity. A growing number of published studies reflects the efforts made in the search for new antifungal proteins and peptides (AFPs), their efficacy, species specificity and applicability. In this review, we discuss important aspects related to fungi, their impact on our life and issues involved in treating fungal infections in plants, animals and humans. We specifically highlight the potential of AFPs from Eurotiales as promising alternative antifungal therapeutics. This article provides insight into the structural features, mode of action, and progress made toward their potential application in a clinical and agricultural setting. It also identifies the challenges that must be overcome in order to develop AFPs into therapeutics.

Antifungal activity of β-lapachone against a fluconazole-resistant Candida auris strain

Candida spp. can be found in the human microbiome. However, immunocompromised patients are likely to develop invasive Candida infections, with mortality rates higher than 50%. The discovery of C. auris, a species that rapidly acquire antifungal resistance, increased the concern about Candida infections. The limited number of antifungal agents and the high incidence of resistance to them make imperative the development of new antifungal drugs. β-lapachone is a biological active naphthoquinone that displays antifungal activity against C. albicans and C. glabrata. The aim of this study was to evaluate if this substance affects C. auris growth and elucidate its mechanism of action. A fluconazole-resistant C. auris isolate was used in this study. The antifungal activity of β-lapachone was determined through microbroth dilution assays, and its mechanism of action was evaluated using fluorescent probes. Interaction with fluconazole and amphotericin B was assessed by disk diffusion assay and checkerboard. β-lapachone inhibited planktonic C. auris cell growth by 92.7%, biofilm formation by 84.9%, and decrease the metabolism of preformed biofilms by 87.1% at 100 µg/ml. At 100 µg/ml, reductions of 30% and 59% of Calcofluor White and Nile red fluorescences were observed, indicating that β-lapachone affects cell wall chitin and neutral lipids content, respectively. Also, the ratio 590 nm/529 nm of JC-1 decreased 52%, showing that the compound affects mitochondria. No synergism was observed between β-lapachone and fluconazole or amphotericin B. Data show that β-lapachone may be a promising candidate to be used as monotherapy to treat C. auris resistant 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.

Comprehensive Overview of Candida auris: An Emerging Multidrug-Resistant Fungal Pathogen

The rise of Candida auris, a multidrug-resistant fungal pathogen, across more than 40 countries, has signaled an alarming threat to global health due to its significant resistance to existing antifungal therapies. Characterized by its rapid spread and robust drug resistance, C. auris presents a critical challenge in managing infections, particularly in healthcare settings. With research on its biological traits and genetic basis of virulence and resistance still in the early stages, there is a pressing need for a concerted effort to understand and counteract this pathogen. This review synthesizes current knowledge on the epidemiology, biology, genetic manipulation, pathogenicity, diagnostics, and resistance mechanisms of C. auris, and discusses future directions in research and therapeutic development. By exploring the complexities surrounding C. auris, we aim to underscore the importance of advancing research to devise effective control and treatment strategies.

Candida auris-a systematic review to inform the world health organization fungal priority pathogens list

The World Health Organization (WHO) in 2022 developed a fungal priority pathogen list. Candida auris was ultimately ranked as a critical priority pathogen. PubMed and Web of Science were used to find studies published from 1 January 2011 to 18 February 2021, reporting on predefined criteria including: mortality, morbidity (i.e., hospitalization and disability), drug resistance, preventability, yearly incidence, and distribution/emergence. Thirty-seven studies were included in the final analysis. The overall and 30-day mortality rates associated with C. auris candidaemia ranged from 29% to 62% and 23% to 67%, respectively. The median length of hospital stay was 46-68 days, ranging up to 140 days. Late-onset complications of C. auris candidaemia included metastatic septic complications. Resistance rates to fluconazole were as high as 87%-100%. Susceptibility to isavuconazole, itraconazole, and posaconazole varied with MIC90 values of 0.06-1.0 mg/l. Resistance rates to voriconazole ranged widely from 28% to 98%. Resistance rates ranged between 8% and 35% for amphotericin B and 0%-8% for echinocandins. Over the last ten years, outbreaks due to C. auris have been reported in in all WHO regions. Given the outbreak potential of C. auris, the emergence and spread of MDR strains, and the challenges associated with its identification, and eradication of its environmental sources in healthcare settings, prevention and control measures based on the identified risk factors should be evaluated for their effectiveness and feasibility. Global surveillance studies could better inform the incidence rates and distribution patterns to evaluate the global burden of C. auris infections.

Candida auris Outbreaks: Current Status and Future Perspectives

Candida auris has been identified by the World Health Organization (WHO) as a critical priority pathogen on its latest list of fungi. C. auris infections are reported in the bloodstream and less commonly in the cerebrospinal fluid and abdomen, with mortality rates that range between 30% and 72%. However, no large-scale epidemiology studies have been reported until now. The diagnosis of C. auris infections can be challenging, particularly when employing conventional techniques. This can impede the early detection of outbreaks and the implementation of appropriate control measures. The yeast can easily spread between patients and in healthcare settings through contaminated environments or equipment, where it can survive for extended periods. Therefore, it would be desirable to screen patients for C. auris colonisation. This would allow facilities to identify patients with the disease and take appropriate prevention and control measures. It is frequently unsusceptible to drugs, with varying patterns of resistance observed among clades and geographical regions. This review provides updates on C. auris, including epidemiology, clinical characteristics, genomic analysis, evolution, colonisation, infection, identification, resistance profiles, therapeutic options, prevention, and control.

Potential Activity of Micafungin and Amphotericin B Co-Encapsulated in Nanoemulsion against Systemic Candida auris Infection in a Mice Model

The Candida auris species is a multidrug-resistant yeast capable of causing systemic and lethal infections. Its virulence and increase in outbreaks are a global concern, especially in hospitals where outbreaks are more recurrent. In many cases, monotherapy is not effective, and drug combinations are opted for. However, resistance to antifungals has increased over the years. In view of this, nanoemulsions (NEs) may represent a nanotechnology strategy in the development of new therapeutic alternatives. Therefore, this study developed a co-encapsulated nanoemulsion with amphotericin B (AmB) and micafungin (MICA) (NEMA) for the control of infections caused by C. auris. NEs were developed in previous studies. Briefly, the NEs were composed of a mixture of 10% sunflower oil and cholesterol as the oil phase (5:1), 10% Polyoxyethylene (20) cetyl ether (Brij® 58) and soy phosphatidylcholine as surfactant/co-surfactant (2:1), and 80% PBS as the aqueous phase. The in vivo assay used BALB/c mice weighing between 25 and 28 g that were immunosuppressed (CEUA/FCF/CAr n° 29/2021) and infected with Candida auris CDC B11903. The in vivo results show the surprising potentiate of the antifungal activity of the co-encapsulated drugs in NE, preventing yeast from causing infection in the lung and thymus. Biochemical assays showed a higher concentration of liver and kidney enzymes under treatment with AmB and MICAmB. In conclusion, this combination of drugs to combat the infection caused by C. auris can be considered an efficient therapeutic option, and nanoemulsions contribute to therapeutic potentiate, proving to be a promising new alternative.

Skin and hard surface disinfection against Candida auris - What we know today

Candida auris has emerged as a global healthcare threat, displaying resistance to important healthcare antifungal therapies. Infection prevention and control protocols have become paramount in reducing transmission of C. auris in healthcare, of which cleaning and disinfection plays an important role. Candida albicans is used as a surrogate yeast for yeasticidal claims of disinfection products, but reports have been made that sensitivity to disinfectants by C. auris differs from its surrogate. In this review, we aimed to compile the information reported for products used for skin and hard surface disinfection against C. auris in its planktonic or biofilm form. A comparison was made with other Candida species, and information were gathered from laboratory studies and observations made in healthcare settings.

Finding Candida auris in public metagenomic repositories

Candida auris is a newly emerged multidrug-resistant fungus capable of causing invasive infections with high mortality. Despite intense efforts to understand how this pathogen rapidly emerged and spread worldwide, its environmental reservoirs are poorly understood. Here, we present a collaborative effort between the U.S. Centers for Disease Control and Prevention, the National Center for Biotechnology Information, and GridRepublic (a volunteer computing platform) to identify C. auris sequences in publicly available metagenomic datasets. We developed the MetaNISH pipeline that uses SRPRISM to align sequences to a set of reference genomes and computes a score for each reference genome. We used MetaNISH to scan ~300,000 SRA metagenomic runs from 2010 onwards and identified five datasets containing C. auris reads. Finally, GridRepublic has implemented a prospective C. auris molecular monitoring system using MetaNISH and volunteer computing.

Efficacy of the combination of amphotericin B and echinocandins against Candida auris in vitro and in the Caenorhabditis elegans host model

IMPORTANCE

Multidrug resistance is a rising problem among non-Candida albicans species, such as Candida auris. This therapeutic problem has been very important during the COVID-19 pandemic. The World Health Organization has included C. auris in its global priority list of health-threatening fungi, to study this emerging multidrug-resistant species and to develop effective alternative therapies. In the present study, the synergistic effect of the combination of amphotericin B and echinocandins has been demonstrated against blood isolates of C. auris. Different susceptibility responses were also observed between aggregative and non-aggregative phenotypes. The antifungal activity of these drug combinations against C. auris was also demonstrated in the Caenorhabditis elegans host model of candidiasis, confirming the suitability and usefulness of this model in the search for solutions to antimicrobial resistance.

Plastic pollution as a novel reservoir for the environmental survival of the drug resistant fungal pathogen Candida auris

The WHO recently classified Candida auris as a fungal pathogen of "critical concern". Evidence suggests that C. auris emerged from the natural environment, yet the ability of this pathogenic yeast to survive in the natural environment is still poorly understood. The aim of this study, therefore, was to quantify the persistence of C. auris in simulated environmental matrices and explore the role of plastic pollution for facilitating survival and potential transfer of C. auris. Multi-drug resistant strains of C. auris persisted for over 30 days in river water or seawater, either planktonically, or in biofilms colonising high-density polyethylene (HDPE) or glass. C. auris could be transferred from plastic beads onto simulated beach sand, particularly when the sand was wet. Importantly, all C. auris cells recovered from plastics retained their pathogenicity; therefore, plastic pollution could play a significant role in the widescale environmental dissemination of this recently emerged pathogen.

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.

An Overview on Candida auris in Healthcare Settings

Candida auris has become a major concern in critical care medicine due to the increasing number of immunocompromised patients and candidiasis is the most frequent cause of fungal infections. C. auris and other fungal pathogens are responsible for at least 13 million infections and 1.5 million deaths globally per year. In immunocompromised patients, infections can quickly become severe, causing wound infections, otitis and candidemia, resulting in high morbidity and mortality. The clinical presentation of C. auris is often non-specific and similar to other types of systemic infections; in addition, it is harder to identify from cultures than other, more common types of Candida spp. Some infections are particularly difficult to treat due to multi-resistance to several antifungal agents, including fluconazole (and other azoles), amphotericin B and echinocandins. This entails treatment with more drugs and at higher doses. Even after treatment for invasive infections, patients generally remain colonized for long periods, so all infection control measures must be followed during and after treatment of the C. auris infection. Screening patients for C. auris colonization enables facilities to identify individuals with C. auris colonization and to implement infection prevention and control measures. This pathogenic fungus shows an innate resilience, enabling survival and persistence in healthcare environment and the ability to rapidly colonize the patient's skin and be easily transmitted within the healthcare setting, thus leading to a serious and prolonged outbreak.

Host defense mechanisms against Candida auris

INTRODUCTION

Candida auris is a pathogen of growing public health concern given its rapid spread across the globe, its propensity for long-term skin colonization and healthcare-related outbreaks, its resistance to a variety of antifungal medications, and the high morbidity and mortality associated with invasive disease. Despite that, the host immune response mechanisms that operate during C. auris skin colonization and invasive infection remains poorly understood.

AREAS COVERED

In this manuscript, we review the available literature in the growing research field pertaining to C. auris host defenses and we discuss what is known about the ability of C. auris to thrive on mammalian skin, the role of lymphoid cell-mediated, IL-17-dependent defenses in controlling cutaneous colonization, and the contribution of myeloid phagocytes in curtailing systemic infection.

EXPERT OPINION

Understanding the mechanisms by which the host immune system responds to and controls colonization and infection with C. auris and developing a deeper knowledge of tissue-specific host-C. auris interactions and of C. auris immune-evading mechanisms may help devise improved strategies for decolonization, prognostication, prevention, vaccination, and/or directed antifungal treatment in vulnerable patient populations.