What is: Candida auris

Scientific Frontline: Extended "At a Glance" Summary: Candida auris

The Core Concept: Candida auris is an emerging, multidrug-resistant pathogenic fungus that presents a critical threat in clinical settings due to its unprecedented ability to colonize human skin, survive on abiotic healthcare surfaces for extended periods, and systematically evade all three major classes of traditional antifungal therapeutics.

Key Distinction/Mechanism: Unlike traditional opportunistic fungal pathogens such as Candida albicans, C. auris behaves with the aggressive transmissibility of a bacterial superbug, utilizing unique evolutionary adaptations—such as the formation of giant lipid droplets (gLDs) and the use of the novel cationic adhesin Scf1—to persist on dry, synthetic surfaces and bypass innate immune detection via cell wall mannosylation that suppresses NETosis.

Origin/History: First identified in the external ear canal of a patient in Japan in 2009, C. auris simultaneously emerged as a human pathogen across multiple, geographically isolated continents, a phenomenon currently attributed to the global warming emergence hypothesis which posits that anthropogenic climate change forced the thermal adaptation of this historically non-pathogenic environmental saprophyte.

Major Frameworks/Components:

• Six globally distinct phylogeographic clades (South Asian, East Asian, African, South American, Iranian, Indomalayan) resulting from isolated genetic drift.
• Innate immune evasion via cell wall mannosylation masking underlying \(\beta\)-glucans from Dectin-1 receptors, inhibiting neutrophil recruitment and NETosis.
• Sophisticated, clade-specific antifungal resistance mechanisms, including target site mutations (ERG11, FKS1), efflux pump amplification (Cdr1/TAC1b), and \(\beta\)-1,6-glucan compensatory upregulation during echinocandin stress.

Candida auris Therapeutic Target Discovered

Candida auris is the first fungus to spread in hospitals and is resistant to all three major classes of antifungal drugs. New research has discovered that the elimination of a single gene stops the fungus from growing — which could lead to an effective drug treatment.
Photo Credit: CDC
(Public Domain)

Scientific Frontline: Extended "At a Glance" Summary: Therapeutic Target for Candida auris

The Core Concept: Researchers have identified the TRK1 gene and its corresponding protein transporter as essential for potassium uptake in the multidrug-resistant fungus Candida auris, presenting a novel therapeutic target to halt its growth and prevent skin colonization.

Key Distinction/Mechanism: While most fungal cellular machinery closely resembles human eukaryotic structures, the TRK1 potassium transporter in C. auris has no structural counterpart in animal cells. This biological divergence allows for the development of targeted antifungal inhibitors that disrupt fungal colonization without inducing toxicity in human tissues.

Major Frameworks/Components:

• Candida auris Skin Colonization: The pathogenic process of the yeast establishing itself on human epithelial surfaces prior to internal infection.
• Potassium Transport Pathways: The biological dependency of the fungus on external potassium for sustained cellular growth, mediated by the Trk1 protein.
• Gene Deletion Mutagenesis: The experimental methodology used to isolate TRK1 function, demonstrating that the elimination of this single gene stops fungal proliferation.
• Eukaryotic Structural Divergence: The comparative biological framework highlighting the unique structure of the fungal TRK1 transporter versus animal cells, providing a safe pharmacological target.

Candida auris: Harbinger of Fungal Pathogens

A microbiological culture of the yeast Candida auris which can be responsible for infections.
Image Credit: Scientific Frontline / AI generated

Scientific Frontline: Extended "At a Glance" Summary: Candida auris

The Core Concept: Candida auris is an emerging, multidrug-resistant pathogenic yeast capable of causing life-threatening invasive infections in humans, serving as a potential harbinger of other climate-adapted fungal pathogens.

Key Distinction/Mechanism: Unlike most fungal species that cannot survive at normal human body temperatures, Candida auris thrives at 37 degrees Celsius and up to 47 degrees Celsius—a thermal tolerance hypothesized to be driven by climate change or anthropogenic environmental shifts—while also persisting on hospital surfaces and resisting multiple antifungal medications.

Origin/History: First discovered in 2009 in a patient's ear in Japan (hence the name auris, meaning ear), the fungus subsequently emerged simultaneously across multiple distinct genetic lineages on several continents, indicating a globally active selective pressure.

Major Frameworks/Components:

• Thermal Adaptation Hypothesis: The theoretical model proposing that rising global temperatures select for thermotolerant fungi capable of overcoming the mammalian 37-degree Celsius thermal barrier.
• Clinical Severity and Mortality: Documenting bloodstream infection mortality rates ranging from 20% to 67% (averaging around 52% globally) in immunocompromised hospital and care-home patients.
• Integrated Early-Warning Systems: Frameworks emphasizing systematic surveillance of fungi in soil, water, air, and healthcare facilities through the collaboration of environmental monitoring, climate research, evolutionary biology, and medicine.

Resistant mushroom species spreads

Candida auris infections are difficult to treat and potentially life-threatening. The picture shows yeast cells from C. auris on the left and a fluconazole-resistant C. auris strain on the right.
Image Credit: Alexander Aldejohann

Scientific Frontline: Extended "At a Glance" Summary: Candida auris

The Core Concept: Candida auris is an emerging, multidrug-resistant species of yeast capable of causing severe, potentially life-threatening invasive infections in humans.

Key Distinction/Mechanism: Unlike most other Candida species, C. auris efficiently spreads from person to person through direct and indirect contact, leading to hospital outbreaks that are exceptionally difficult to control. It also demonstrates high resistance to multiple classes of antifungal medications, including fluconazole and echinocandins.

Origin/History: The species was first formally described in 2009, with no known scientific evidence of its existence prior to the 1990s, leaving the ecological niche it previously occupied a mystery.

Major Frameworks/Components:

• Antifungal Resistance: The pathogen's ability to withstand treatment from established antifungal classes, complicating therapeutic interventions and driving clinical prioritization.
• Nosocomial Transmission: The mechanism by which the fungus efficiently transfers among patients within medical facilities, such as hospitals, outpatient practices, and nursing homes.
• Epidemiological Surveillance: The systematic tracking of clinical cases, colonization events, and transmission vectors by institutions like the Robert Koch Institute to guide infection control responses.

Synthetic Sugar Fights Drug-Resistant Candida auris Fungus

Candida Auris
Image Credit: Scientific Frontline / stock image

Scientific Frontline: Extended "At a Glance" Summary: Synthetic Sugar Molecule against Candida auris

The Core Concept: Researchers have synthesized a specific sugar molecule, a β-mannan tetrasaccharide, that mimics a natural component of the cell wall of the multidrug-resistant fungus Candida auris, to trigger a targeted immune response.

Key Distinction/Mechanism: Instead of purifying complex and variable sugar structures directly from the fungal cell wall, scientists chemically synthesized a precise four-block sugar structure in the laboratory. By linking this synthetic sugar to a carrier protein (creating a glycoconjugate), they successfully directed the immune system to recognize and attack the fungus.

Major Frameworks/Components:

• Chemical Synthesis: Laboratory creation of a precise β-mannan tetrasaccharide to ensure a defined composition, avoiding the variability of natural fungal cell walls.
• Glycoconjugation: Linking the synthetic sugar molecule to a carrier protein to enhance the immune system's ability to recognize the sugar and mount a response.
• Passive Immunization: Developing specific antibodies that recognize the sugar structure to neutralize the pathogen directly.
• Diagnostic Application: Utilizing the generated antibodies to create a rapid lateral flow test (similar to a COVID-19 or pregnancy test) for quick detection of the fungus.

What Are Fungal Priority Pathogens? The Rise of Candida auris

A strain of Candida auris cultured in a petri dish at a CDC laboratory.
Photo Credit: Shawn Lockhart / Centers for Disease Control / Public Domain

Scientific Frontline: Extended "At a Glance" Summary: Fungal Priority Pathogens and Candida auris

The Core Concept: Fungal infections represent a significant, increasing, and often deadly threat to global public health, prompting the World Health Organization (WHO) to publish its first-ever list of fungal "priority pathogens," which catalogs the 19 fungi most dangerous to humans.

Key Distinction/Mechanism: While fungal infections traditionally targeted severely ill or immunosuppressed individuals, rising ambient global temperatures are allowing certain deadly fungi, such as the drug-resistant yeast Candida auris, to adapt, overcome mammalian body temperature defenses, and transmit efficiently between humans.

Origin/History: The WHO published its inaugural priority pathogen list in late 2022 to address the severe lack of global research and development funding directed toward fungal treatments; notably, C. auris was completely unknown in human infections prior to 2009.

Major Frameworks/Components:

• Pathogen Prioritization: The WHO's strategic classification of fungi to direct global attention, specifically categorizing C. auris as a "critical priority" pathogen due to its high mortality rate and rapid global emergence.
• Climate-Driven Adaptation: The evolutionary hypothesis proposing that as global ambient temperatures rise, fungal species adapt to survive at higher temperatures, circumventing the thermal barrier naturally provided by the normal human body temperature.
• Nosocomial Transmission: The alarming shift of specific fungi, like C. auris, from opportunistic environmental hazards to pathogens capable of rapid, direct patient-to-patient transmission within healthcare settings, such as intensive care units.

Monash researchers on the front line in fight against fungal infections

The fungal pathogen Candida albicans transformed with a green fluorescence protein (GFP) tagged iron sensor is engulfed by macrophages. Upon iron starvation induced by macrophages Candida will express GFP and make hyphal projections thereby escaping immune cells.
Source: Monash University

With fungal infections killing 1.5 million people each year, Monash University researchers are playing an important role as the World Health Organization recognizes this growing threat.

The world-leading Monash experts are among a small but determined group of researchers working to curb the growing impact of potentially dangerous fungal infections.

In late October, 2022, WHO published a report highlighting the first list of fungal "priority pathogens" – a catalogue of the 19 fungi that represent the greatest threat to public health.

The premise behind the publication is twofold: fungi are a significant and increasing threat to public health, and because there is little global research and development into fungi or their treatment.

Professor Ana Traven, from the Monash Biomedicine Discovery Institute, said fungi could range from benign (skin and nail infections and vaginal thrush) to the deadly (Candida, Aspergillus).

Researchers find deadly fungus can multiply by having sex, which could produce more drug-resistant, virulent strains

 Jianping Xu, professor in McMaster University’s
Department of Biology and researcher with Canada’s
Global Nexus for Pandemics and Biological Threats
Credit: McMaster University

Researchers at McMaster University have unlocked an evolutionary mystery of a deadly pathogen responsible for fueling the superbug crisis: it can reproduce by having sex.

And while such fraternizing is infrequent, scientists report it could be producing more drug-resistant and more virulent strains of Candida auris, capable of spreading faster.

C. auris is a fungus that can cause severe infections and sometimes death, often striking immunocompromised hospital patients.

Unlike animals and plants, microorganisms of this nature usually divide and reproduce asexually, so one produces two, two produce four and so on, all genetically identical to each other, through a process of very simple division and without the exchange of genetic material.

“One of the really complex and puzzling questions about this fungal pathogen is its origin and how it reproduces in nature,” says Jianping Xu, a professor in McMaster’s Department of Biology and researcher with Canada’s Global Nexus for Pandemics and Biological Threats.

For the study, recently published online in Computation and Structural Biotechnology Journal, researchers analyzed nearly 1,300 strains available on a public database of C. auris genome sequences. They searched for and confirmed recombination events, or sexual activity.

The findings will help to further research because scientists can now replicate those sexual behaviors in the lab.

“The research tells us that this fungus has been recombined in the past and can recombine in nature, which enables it to generate new genetic variants rather quickly,” explains Xu. “That may sound frightening, but it’s a double-edged sword. Because we learned they could recombine in nature, we could possibly replicate the process in the lab, which could allow us to understand the genetic controls of virulence and drug resistance and potentially other traits that make it such a dangerous pathogen, much faster.”

The Skin Microbiome: A New Antimicrobial Source

McMaster University researcher Lindsay Kalan (right) and MSc student Jordana Ferro examine a dish containing skin-associated bacteria.
Photo Credit: Courtesy of McMaster University

Scientific Frontline: Extended "At a Glance" Summary: The Skin Microbiome as an Antimicrobial Reservoir

The Core Concept: The human skin microbiome constitutes a vast, diverse community of bacteria, fungi, and viruses that acts as a protective barrier against external pathogens. Recent research indicates that these endogenous microbial populations naturally produce novel antimicrobial compounds to defend their host.

Key Distinction/Mechanism: Unlike traditional antibiotic discovery, which typically relies on isolating microbes from environmental soil samples, this framework investigates the human body's native flora. Certain newly discovered skin-associated bacterial species act as "fungal specialists," synthesizing previously uncharacterized chemical molecules to directly inhibit drug-resistant pathogens.

Major Frameworks/Components:

• Epithelial Isolate Collection (EPIC): A comprehensive microbial library gathered from eight distinct microenvironments on the human body, representing an estimated 95 percent of the entire human skin microbiome.
• Biosynthetic Gene Clusters: Genetic sequences responsible for producing antimicrobial chemicals. Analysis revealed that 96 percent of the identified clusters in these specific skin microbes remain uncharacterized, suggesting immense potential for novel molecular discovery.
• Fungal Specialists: Three of the newly discovered bacterial species demonstrate a highly effective ability to deter severe, drug-resistant fungal pathogens, including Candida auris and species within the Cryptococcus genus.
• Broad-Spectrum Defense: Validation experiments confirmed that these skin microbes possess chemical defenses active against over 20 human pathogens, including Escherichia coli and Staphylococcus aureus.