Development and standardization of a specific real-time PCR assay for the rapid detection of Candida auris

Emergence of Candida auris in intensive care units in Algeria

Background

Currently, Candida auris is among the most serious emerging pathogens that can be associated with nosocomial infections and outbreaks in intensive care units. Clinicians must be able to identify and manage it quickly.

Objective

Here, we report for the first time in Algeria seven cases of C. auris infection or colonisation.

Methods and Results

The strains were isolated from clinical sites including bronchial aspirates (n = 4), wound swabs (n = 1), urine sample (n = 1) and peritoneal fluid (n = 1), in patients admitted to the intensive care unit. Candida auris was identified both by MALDI‐TOF and by sequencing the ITS region and the D1/D2 domain. Antifungal susceptibility testing was performed using the E‐test method. Non‐wildtype susceptibility was observed for five strains against fluconazole, itraconazole, voriconazole and caspofungin. Genotyping showed the presence of four clades (I–IV) in one hospital.

Conclusions

Appropriate antifungal treatments with rapid and accurate microbial identification are the cornerstone for the management and control of C. auris infections.

Expert recommendations for prevention and management of Candida auris transmission

Candida auris was first described as a yeast pathogen in 2009. Since then, the new species has emerged worldwide. In contrast to most other Candida spp., C. auris frequently exhibits multi-drug resistance and is readily transmitted in hospital settings. While most isolations so far are from colonized patients, C. auris does cause life-threatening invasive infections. During management of the first documented C. auris transmission in a German hospital, experts from the National Reference Centers for Invasive Fungal Infections (NRZMyk) and the National Reference Center for Surveillance of Nosocomial Infections screened available literature and integrated available knowledge on infection prevention and C. auris epidemiology and biology to enable optimal containment. Relevant recommendations developed during this process are summarized in this guidance document, intended to assist in management of C. auris transmission and potential outbreak situations. Rapid and effective measures to contain C. auris spread require a multidisciplinary approach that includes clinical specialists of the affected unit, nursing staff, hospital hygiene, diagnostic microbiology, cleaning staff, hospital management and experts in diagnostic mycology / fungal infections. Action should be initiated in a step-wise process and relevant interventions differ between management of singular C. auris colonized / infected patients and detection of potential C. auris transmission or nosocomial outbreaks. [word count 205].

Tools for detecting a "superbug": updates on Candida auris testing

Candida auris is an emerging yeast species that has the unique characteristics of patient skin colonization and rapid transmission within healthcare facilities and the ability to rapidly develop antifungal resistance. When C. auris first started appearing in clinical microbiology laboratories, it could only be identified using DNA sequencing. In the decade since its first identification outside of Japan there have been many improvements in the detection of C. auris. These include the expansion of MALDI-TOF databases to include C. auris, the development of both laboratory-developed tests and commercially available kits for its detection, and special CHROMagar for identification from laboratory specimens. Here we discuss the current tools and resources that are available for C. auris identification and detection.

Adapted Protocol for Saccharibacteria Cocultivation: Two New Members Join the Club of Candidate Phyla Radiation

The growing application of metagenomics to different ecological and microbiome niches in recent years has enhanced our knowledge of global microbial biodiversity. Among these abundant and widespread microbes, the candidate phyla radiation (CPR) group has been recognized as representing a large proportion of the microbial kingdom (>26%). CPR are characterized by their obligate symbiotic or exoparasitic activity with other microbial hosts, mainly bacteria. Currently, isolating CPR is still considered challenging for microbiologists. The idea of this study was to develop an adapted protocol for the coculture of CPR with a suitable bacterial host. Based on various sputum samples, we tried to enrich CPR (Saccharibacteria members) and to cocultivate them with pure hosts (Schaalia odontolytica). This protocol was monitored by TaqMan real-time quantitative PCR (qPCR) using a system specific for Saccharibacteria designed in this study, as well as by electron microscopy and sequencing. We succeeded in coculturing and sequencing the complete genomes of two new Saccharibacteria species, "Candidatus Minimicrobia naudis" and "Candidatus Minimicrobia vallesae." In addition, we noticed a decrease in the C_T values of Saccharibacteria and a significant multiplication through their physical association with Schaalia odontolytica strains in the enriched medium that we developed. This work may help bridge gaps in the genomic database by providing new CPR members, and in the future, their currently unknown characteristics may be revealed. IMPORTANCE In this study, the first TaqMan real-time quantitative PCR (qPCR) system, targeting Saccharibacteria phylum, has been developed. This technique can specifically quantify Saccharibacteria members in any sample of interest in order to investigate their prevalence. In addition, another easy, specific, and sensitive protocol has been developed to maintain the viability of Saccharibacteria cells in an enriched medium with their bacterial host. The use of this protocol facilitates subsequent studies of the phenotypic characteristics of CPR and their physical interactions with bacterial species, as well as the sequencing of new genomes to improve the current database.

So Many Diagnostic Tests, So Little Time: Review and Preview of Candida auris Testing in Clinical and Public Health Laboratories

The recognition of a new yeast, Candida auris, in 2009 in East Asia, and its rapid global spread, was a reminder of the threats posed by multidrug-resistant fungal pathogens. C. auris had likely remained unrecognized for a long time as accurate tests were not available. The laboratory community responded to the C. auris challenge by publishing 35 new or revised diagnostic methods between 2014 and early 2021. The commercial sector also modified existing diagnostic devices. These C. auris diagnostic tests run the gamut from traditional culture-based differential and selective media, biochemical assimilations, and rapid protein profiles, as well as culture-independent DNA-based diagnostics. We provide an overview of these developments, especially the tests with validation data that were subsequently adopted for common use. We share a workflow developed in our laboratory to process over 37,000 C. auris surveillance samples and 5,000 C. auris isolates from the outbreak in the New York metropolitan area. Our preview covers new devices and diagnostic approaches on the horizon based on microfluidics, optics, and nanotechnology. Frontline laboratories need rapid, cheap, stable, and easy-to-implement tests to improve C. auris diagnosis, surveillance, patient isolation, admission screening, and environmental control. Among the urgent needs is a lateral flow assay or similar device for presumptive C. auris identification. All laboratories will benefit from devices that allow rapid antifungal susceptibility testing, including detection of mutations conferring drug resistance. Hopefully, multiplex test panels are on the horizon for synergy of C. auris testing with ongoing surveillance of other healthcare-associated infections. C. auris genome analysis has a proven role for outbreak investigations, and diagnostic laboratories need quick access to regional and national genome analysis networks.

Metagenomic Sequencing for Direct Identification of Candida auris Colonization

Candida auris is an emerging multidrug-resistant yeast that is associated with skin colonization and deadly bloodstream infections, especially in ventilator skilled nursing facilities. An ongoing question is how this organism colonizes the skin of these patients and whether the skin microbiome provides a measure of colonization resistance against C. auris. Now, Huang et al. (X. Huang, R. M. Welsh, C. Deming, D. M. Proctor, et al., mSphere 6:e00287-21, 2021, https://doi.org/10.1128/mSphere.00287-21) demonstrate a method for shotgun metagenomic analysis of the skin to generate a profile of fungal colonization that is highly correlative with culture-based methods. These methods are likely to assist in the diagnosis of C. auris and the identification of microbiome-associated risk factors that predict invasive disease.

SCA Medium: A New Culture Medium for the Isolation of All Candida auris Clades

Candida auris is an emerging multidrug-resistant yeast causing nosocomial infections and associated with high mortality in immunocompromised patients. Rapid identification and characterisation are necessary for diagnosis and containing its spread. In this study, we present a selective culture medium for all C. auris clades. This medium is sensitive with a limit of detection ranging between 10¹ and 10² CFU/mL. The 100% specificity of SCA (specific C. auris) medium is confirmed on a set of 135 Candida strains, 50 bacterial species and 200 human stool samples. Thus, this medium specifically selects for C. auris isolation from clinical samples, allowing the latter to study its phenotypic profile.