ClaID: a Rapid Method of Clade-Level Identification of the Multidrug Resistant Human Fungal Pathogen Candida auris

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.

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.

Identification of C. auris clade 5 isolates using claID

Candida auris poses threats to the global medical community due to its multidrug resistance, ability to cause nosocomial outbreaks and resistance to common sterilization agents. Different variants that emerged at different geographical zones were classified as clades. Clade-typing becomes necessary to track its spread, possible emergence of new clades, and to predict the properties that exhibit a clade bias. We previously reported a colony-Polymerase Chain Reaction-based, clade-identification method employing whole genome alignments and identification of clade-specific sequences of four major geographical clades. Here, we expand the panel by identifying clade 5 which was later isolated in Iran, using specific primers designed through in silico analyses.

Description of Candida auris Occurrence in a Tertiary Health Institution in Riyadh, Saudi Arabia

BACKGROUND

Candida auris is an emerging multidrug-resistant fungal pathogen that represents a current serious threat to healthcare settings.

OBJECTIVE

The objective was to determine the prevalence of C. auris in a Riyadh hospital since its initial detection in late 2019.

METHODS

Using an adapted risk assessment tool, we reviewed the charts and medical files of all suspected and confirmed cases of C. auris infections reported at King Khalid University Hospital, Riyadh, between November 2019 and December 2022. Anonymized data were retrieved in a pre-established datasheet and analyzed to determine the epidemiological characteristics of C. auris infections in our facility. We analyzed prevalence by age, gender, risk factors, and according to sampling source.

RESULTS

Of the 53 confirmed C. auris-positive cases during the study period, 33 (62%) were males. Their ages ranged between 15 and 98, with most positive cases occurring in those aged 50 and above. Only one of the confirmed cases was hospital-acquired. All patients had at least one risk factor, and urine samples yielded the greatest number of positive cases, while admission to healthcare facilities constituted the highest risk in our study.

CONCLUSION

Establishing a local prevalence pattern could serve as a baseline/benchmark to compare with regional and international benchmarks.

First report of Candida auris in Romania: clinical and molecular aspects

The emerging opportunistic fungal pathogen Candida auris raises significant concerns for public health due to its outbreak potential, the associated high mortality, increased resistance to antifungals, challenging identification to species level, since commonly used diagnostic methods can confuse this fungus with other Candida spp. The present outbreak report describes probably some of the first Candida auris cases in Romania, providing clinical and epidemiological data, and also whole genome sequencing data. The cases were identified in three hospitals in Bucharest during the first eight months of 2022.

Clonal Diversity of Candida auris, Candida blankii, and Kodamaea ohmeri Isolated from Septicemia and Otomycosis in Bangladesh as Determined by Multilocus Sequence Typing

Candida auris, Candida blankii, and Kodamaea ohmeri have been regarded as emerging fungal pathogens that can cause infections with high mortality. For genotyping of C. auris, a multilocus sequence typing (MLST) scheme based on four locus sequences has been reported, while there is no typing scheme for C. blankii and K. ohmeri. In the present study, the existing MLST scheme of C. auris was modified by adding more locus types deduced from sequence data available in the GenBank database. Furthermore, MLST schemes of C. blankii and K. ohmeri were developed using the four cognate loci (ITS, RPB1, RPB2, D1/D2) and similar sequence regions to those of C. auris. These MLST schemes were applied to identify the ST (sequence type) of clinical isolates of C. auris (n = 7), C. blankii (n = 9), and K. ohmeri (n = 6), derived from septicemia or otomycosis in Bangladesh in 2021. All the C. auris isolates were classified into a single ST (ST5) and clade I, having a Y132F substitution in ERG11p, which is associated with azole resistance. Similarly, all the C. blankii isolates belonged to a single type (ST1). In contrast, six K. ohmeri isolates were assigned to five types (ST1-ST5), suggesting its higher genetic diversity. These findings revealed the availability of MLST schemes for these three fungal species for understanding their clonal diversity among clinical isolates.

A case of fungal otitis externa caused by coinfection of Candida auris and Aspergillus flavus

Fungal otitis externa is a disease encountered occasionally and is caused mostly by Aspergillus or Candida spp. We report a woman with fungal otitis externa who also had typical findings in the external auditory canal. The results of a culture showed coinfection with Candida auris and Aspergillus flavus. Identification of both species was performed by sequencing analysis of the 26S rDNA (D1/D2) region. Additionally, the newly developed CHROMagar™ Candida Plus medium was a useful tool for the easy and rapid identification of C. auris. To the best of our knowledge, this is the first report of fungal otitis externa caused by coinfection with C. auris and A. flavus. This case showed good susceptibility to many antifungal drugs and fortunately had a good clinical course with 1% bifonazole cream, which was applied to the fungal coinfection. Notably, C. auris is a multidrug-resistant yeast-like fungus. The increase in drug-resistant fungi and co-infections caused by these pathogens can make the diagnosis and treatment more complex and difficult. To solve these problems, performing rapid and accurate identification and susceptibility testing using chromogenic medium and molecular biological analysis would be useful.

Strategies to Prevent Transmission of Candida auris in Healthcare Settings

Purpose of Review

Candida auris, a recently recognized yeast pathogen, has become a major public health threat due to the problems associated with its accurate identification, intrinsic and acquired resistance to antifungal drugs, and its potential to easily contaminate the environment causing clonal outbreaks in healthcare facilities. These outbreaks are associated with high mortality rates particularly among older patients with multiple comorbidities under intensive care settings. The purpose of this review is to highlight strategies that are being adapted to prevent transmission of C. auris in healthcare settings.

Recent Findings

Colonized patients shed C. auris into their environment which contaminates surrounding equipment. It resists elimination even by robust decontamination procedures and is easily transmitted to new patients during close contact resulting in outbreaks. Efforts are being made to rapidly identify C. auris-infected/C. auris-colonized patients, to determine its susceptibility to antifungals, and to perform effective cleaning and decontamination of the environment and isolation of colonized patients to prevent further transmission.

Summary

Rapid and accurate identification of hospitalized patients infected/colonized with C. auris, rapid detection of its susceptibility patterns, and appropriate use of infection control measures can help to contain the spread of this highly pathogenic yeast in healthcare settings and prevent/control outbreaks.

Raman Metabolomics of Candida auris Clades: Profiling and Barcode Identification

This study targets on-site/real-time taxonomic identification and metabolic profiling of seven different Candida auris clades/subclades by means of Raman spectroscopy and imaging. Representative Raman spectra from different Candida auris samples were systematically deconvoluted by means of a customized machine-learning algorithm linked to a Raman database in order to decode structural differences at the molecular scale. Raman analyses of metabolites revealed clear differences in cell walls and membrane structure among clades/subclades. Such differences are key in maintaining the integrity and physical strength of the cell walls in the dynamic response to external stress and drugs. It was found that Candida cells use the glucan structure of the extracellular matrix, the degree of α-chitin crystallinity, and the concentration of hydrogen bonds between its antiparallel chains to tailor cell walls’ flexibility. Besides being an effective ploy in survivorship by providing stiff shields in the α–1,3–glucan polymorph, the α–1,3–glycosidic linkages are also water-insoluble, thus forming a rigid and hydrophobic scaffold surrounded by a matrix of pliable and hydrated β–glucans. Raman analysis revealed a variety of strategies by different clades to balance stiffness, hydrophobicity, and impermeability in their cell walls. The selected strategies lead to differences in resistance toward specific environmental stresses of cationic/osmotic, oxidative, and nitrosative origins. A statistical validation based on principal component analysis was found only partially capable of distinguishing among Raman spectra of clades and subclades. Raman barcoding based on an algorithm converting spectrally deconvoluted Raman sub-bands into barcodes allowed for circumventing any speciation deficiency. Empowered by barcoding bioinformatics, Raman analyses, which are fast and require no sample preparation, allow on-site speciation and real-time selection of appropriate treatments.