Candida auris PCR-Directly on Clinical Samples: Introduction, Principle, Clinical Significance, and Keynotes

Introduction

Candida auris is an emerging multidrug-resistant yeast responsible for outbreaks of healthcare-associated infections worldwide. It is difficult to identify by conventional culture and biochemical methods, often misidentified as other Candida species (C. haemulonii, C. famata). Rapid and accurate detection is essential to initiate infection control measures and guide therapy. PCR-based assays performed directly on clinical samples (blood, urine, swabs, respiratory secretions) have become a valuable diagnostic tool, bypassing the delays of culture.

Principle

• Targeted Gene Amplification:
  • PCR assays amplify species-specific DNA sequences such as the ITS region, D1/D2 domain of 28S rDNA, or unique C. auris-specific gene markers.
• Direct Testing from Clinical Samples:
  • Nucleic acids are extracted directly from patient specimens without the need for culture.
• Amplification & Detection:
  • Real-time PCR (qPCR) with fluorescent probes allows rapid detection within hours.
  • Multiplex PCR can distinguish C. auris from closely related species.
• Controls: Internal amplification controls ensure assay validity and minimize false negatives.

Clinical Significance

• Rapid Diagnosis: Provides results in 3–5 hours compared to days with culture.
• Infection Control: Early detection enables immediate implementation of isolation and decolonization protocols, preventing nosocomial spread.
• Treatment Guidance: Confirms presence of C. auris, allowing clinicians to initiate appropriate antifungal therapy (e.g., echinocandins).
• Epidemiology: Facilitates surveillance of outbreaks and tracking of transmission in healthcare facilities.
• Limitations:
  • Cannot provide antifungal susceptibility data (requires culture).
  • PCR sensitivity may be affected by low fungal burden or sample inhibitors.

Keynotes

• Candida auris is a global health threat due to its multidrug resistance and outbreak potential.
• PCR directly on clinical samples offers rapid, species-specific identification, bypassing misidentification issues of culture-based methods.
• Widely used in the screening of high-risk patients and environmental surveillance in hospitals.
• Works best when combined with culture, MALDI-TOF MS, and antifungal susceptibility testing.
• Remains a critical tool for outbreak control and rapid clinical decision-making in modern mycology.

Further Readings

1. https://www.accessdata.fda.gov/cdrh_docs/reviews/DEN230092.pdf
2. https://www.immy.com/candida-auris-pcr-fungal-test
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC6258843/
4. https://liondx.com/wp-content/uploads/2023/06/Sorveglianza-Candida-auris-RealTime-PCR.pdf
5. https://www.cdc.gov/candida-auris/hcp/laboratories/detection-colonization.html
6. https://www.mdpi.com/2309-608X/6/4/224
7. https://www.sciencedirect.com/science/article/abs/pii/S0195670122001979
8. https://www.cepheid.com/en-GB/insights/insight-hub/tech-disease-trends/2024/09/candida-auris–rising-threat-and-future-implications.html
9. https://www.cdc.gov/candida-auris/hcp/laboratories/real-time-pcr-identification.html
10. https://www.cdc.gov/candida-auris/hcp/screening-hcp/c-auris-screening-patient-swab-collection-1.html
11. https://onlinelibrary.wiley.com/doi/am-pdf/10.1111/myc.70065
12. https://www.cdc.gov/candida-auris/screening/index.html
13. https://www.medrxiv.org/content/10.1101/2020.02.10.20021683.full
14. https://pmc.ncbi.nlm.nih.gov/articles/PMC12048891/
15. https://vitrosens.com/the-rise-of-candida-auris-urgent-threats-and-innovations-in-detection-technology/