News

Candida auris Diagnostics: Molecular and culture-based methods

Candida auris (C. auris) is an emerging, multidrug-resistant yeast associated with rapid outbreaks in healthcare settings, causing invasive, high-mortality infections. Because this fungus is often misidentified, fast and accurate Candida auris diagnostics are essential for outbreak control and patient care. Considering recent outbreaks, this article reviews Candida auris detection methods, including culture and enrichment, Nucleic Acid Amplification Testing (NAATs), MALDI-TOF, antifungal susceptibility testing (AFST), and advanced molecular techniques for Candida auris.

Candida auris clinical relevance

Discovered in 2009 in Japan, Candida auris has become recognized worldwide as a cause of numerous healthcare-associated outbreaks. Unlike other Candida species, it can cause bloodstream and wound infections, often affecting critically ill or immunocompromised patients. The clinical significance of Candida auris also lies in its ability to cause invasive bloodstream and wound infections, mainly in critically ill or immunocompromised patients. Mortality rates are high, partly because of its resistance to multiple antifungal drug classes: this multidrug-resistant profile of Candida auris makes early detection crucial.

Colonization vs. infection

A distinction must be made between colonization and infection:

Colonization: skin or mucosal carriage without symptoms (axilla, groin, nares).
Infection: invasive disease in the blood or tissues with clinical signs.

While colonization contributes to the spread within healthcare settings, invasive infections require specific antifungal treatment guided by antifungal susceptibility testing (AFST. Properly differentiating Candida auris colonization from infection is thus crucial to ensure that only true infections are treated with antifungals, and individuals colonized with Candida auris are managed with infection prevention and control measures to minimize transmission.

**Sample collection and swabbing protocols for Candida auris colonization screening**

Colonized patients act as the primary reservoir for further transmission, making Candida auris colonization screening a key component of hospital outbreak control. Outbreak screening focuses on patients in high-risk wards or transfers from affected facilities. Recommended methods:

Axilla and groin swabs (standard sites).
Composite swabs to increase efficiency.
Additional sites (nares, perianal) for higher sensitivity.
Environmental screening of high-touch hospital surfaces during outbreaks.

Molecular Diagnostics: PCR for Candida auris

Real-time PCR is the fastest and most sensitive method among molecular diagnostics for detecting Candida auris, especially in colonization screening, providing same-day results and enabling quick preventive measures. Although rare, false negatives may occur at low colonization levels, usually due to low fungal load or poor sampling. Labs often confirm positive results with culture for definitive identification and further testing. The use of Candida auris PCR has therefore become central in rapid screening workflows.

Culture and MALDI-TOF identification of Candida auris

Despite a slower turnaround, culture followed by MALDI-TOF identification of Candida auris remains essential for confirming Candida auris isolates from cultures. Although MALDI-TOF analysis itself takes only minutes, colonies need 24–72 hours of growth. Therefore, while MALDI-TOF is not suitable for immediate screening, it remains the gold standard within comprehensive Candida auris diagnostics for definitive identification.

Antifungal susceptibility testing (AFST)

Candida auris shows diverse resistance patterns, making antifungal susceptibility testing (AFST) indispensable. CLSI/EUCAST broth microdilution remains the AFST gold standard, but while precise, these methods are time-consuming. Recently, new techniques, including MALDI-TOF-based AFST and colorimetric assays, have been developed to offer faster results, although they lack standardized clinical breakpoints. Understanding Candida auris resistance patterns is critical to guide targeted therapy.

Protocols for Candida bloodstream infection detection

When patients present with suspected Candida auris bloodstream infection, the workflow typically starts with blood cultures. Routine blood culture systems detect yeast growth but may misidentify C. auris using conventional panels, making confirmation with PCR or MALDI-TOF essential. In conclusion, while molecular assays are critical for making early treatment decisions, culture provides isolates for AFST and pathogen identification within a structured Candida auris diagnostic pathway..

Novel molecular epidemiology and outbreak detection

Whole genome sequencing (WGS) of Candida auris for outbreak analysis is considered the gold standard for identifying clades, mapping transmission, and detecting resistance genes. WGS outbreak analysis supports infection control interventions by clarifying transmission chains. Loop-mediated isothermal amplification (LAMP) assays offer rapid, equipment-light detection with potential application in low-resource settings. Validation studies indicate high sensitivity, though widespread clinical implementation is pending.

Preanalytical and enrichment factors influencing detection

Diagnostic sensitivity in Candida auris detection is heavily influenced by preanalytical variables. Proper swabbing technique, correct transport medium, and rapid delivery to the lab are essential to maintain microorganism viability. Flocked swabs outperform cotton for recovery, and prompt processing prevents DNA degradation. Enrichment culture remains indispensable in outbreak investigations where colonization burden is low or when environmental sampling is undertaken. While enrichment adds time, it provides isolates for definitive identification, AFST, and sequencing.

Global guidance and recommendations

Many guidelines stress the importance of integrating molecular and culture-based diagnostics with coordinated prevention & control strategies for Candida auris outbreaks.

CDC: Advocates PCR for rapid colonization screening, enrichment culture for isolate recovery, and strict implementation of prevention measures.
ECDC: Recommends targeted screening and molecular confirmation, with environmental testing restricted to outbreak contexts.
WHO: Lists C. auris among the top fungal priority pathogens requiring enhanced diagnostics.

Conclusions

Accurate Candida auris diagnostics requires a multimodal diagnostic approach: PCR for rapid screening, culture, and MALDI-TOF for confirmation, AFST for resistance guidance, and WGS for outbreak tracking. Ultimately, effective Candida auris diagnostics combines these methods with the close cooperation among microbiology laboratories, clinicians, and infection prevention teams to contain this multidrug-resistant pathogen.

Resources

Join CoScience HUB

Create your CoScience HUB account now to access cutting-edge science and position yourself at the forefront of innovation.