A silent menace in hospitals worldwide, the yeast Candida auris causes difficult-to-treat, often fatal infections in patients with weakened immune systems. The World Health Organization has tagged C. auris as a high-priority pathogen, notorious for its resistance against rigorous decontamination measures and many antifungal drugs.
To date, researchers have identified five major C. auris clades: genetically-distinct clusters native to specific world regions, with each cluster having its own unique biochemical profiles, transmission pathways and treatment resistance features. Given this complexity, the best C. auris containment strategies rely on good surveillance protocols to trace the origins and spread of infectious strains.
At the A*STAR Genome Institute of Singapore (A*STAR GIS), Associate Director Niranjan Nagarajan, Scientist Chayaporn Suphavilai and PhD student Karrie Ko are among those keeping close tabs on C. auris strains found in Singaporean clinical settings.
“Monitoring clades can help ensure the early detection of new strains with potentially concerning traits, such as a worrying level of virulence or antifungal resistance,” said Suphavilai and Ko.
Three such cases from unrelated patients cropped up in Singapore between 2018 and 2023. These C. auris isolates showed unusual physical traits unlike those of known clades, such as differences in growth patterns, the optimal temperatures at which they survived, and their ability to break down certain chemicals.
Intrigued by such inconsistencies, the researchers wondered whether these samples might belong to a yet-unidentified clade. To investigate, they performed whole genome sequencing (WGS) on the fungal samples, examining small alterations in the DNA called single nucleotide polymorphisms (SNP).
They found that these strains showed differences ranging from 37,000 up to 236,900 SNPs compared with existing C. auris clades listed in global databases. Strikingly, they also responded well to all tested antifungal drugs.
“As the genetic makeup of these new isolates significantly differed from all known C. auris strains, they constitute a new sixth clade—clade VI—with unknown associations and risks,” said Suphavilai and Ko.
When the team examined WGS data from a C. auris isolate from Bangladesh, they found it also fell within clade VI, highlighting the need to further investigate the yeast’s genomic diversity in South and Southeast Asia.
“This discovery highlights C. auris’s dynamic and evolving nature,” Suphavilai and Ko said. “Studying more isolates will be critical to understanding its potential origins, transmission patterns and impact on vulnerable patient populations.”
As reliable prediction of novel threats requires large-scale, high quality genomic data, Suphavilai and Ko also stressed the importance of equipping low- and middle-income countries with the sequencing technologies, training initiatives and financial resources they needed to generate such data from their respective locales.
“Expanding and supporting genomic surveillance efforts in these regions is crucial to ensure the early detection of emerging threats and to safeguard global public health,” the researchers added.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Genome Institute of Singapore (A*STAR GIS).
