Is a blood test used to diagnose Candida auris?

Diagnosis of Candida auris

Blood cultures are the primary diagnostic method for detecting Candida auris, but they are not sufficient as a standalone test due to their limited sensitivity of 50-75% for Candida species detection. 1

Diagnostic Approach for Candida auris

Primary Diagnostic Methods

• Blood cultures remain the gold standard for diagnosing candidemia, including C. auris, but have limitations including slow turnaround time (2-3 days) and moderate sensitivity (50-75%) 1
• For optimal blood culture collection:
  • Collect 3 sets of blood cultures with 40-60 mL total volume for adults 1
  • Use automated validated blood culture systems with at least 5 days of incubation 1
  • Species-level identification is mandatory as treatment varies by Candida species 1

Screening and Detection Methods

• For C. auris screening, composite swabs of axilla and groin are the recommended sampling method 2
• Laboratory testing options include:
  • Specialized salt-containing media or chromogenic agars for culture-based detection 2
  • PCR-based detection methods for more rapid identification 2
• Patients should be considered negative only after 3 consecutive negative screens taken at least 24 hours apart 2

Supplementary Diagnostic Techniques

• Non-culture diagnostic tests can improve and accelerate detection of Candida infections:
  • Combined mannan and anti-mannan antibody detection has 80% sensitivity and 85% specificity for candidemia (though not specific for C. auris) 1
  • β-1,3-D-glucan (BDG) detection serves as a panfungal marker with >65% sensitivity and >80% specificity for candidemia 1
  • Molecular methods such as PCR-based techniques show promise but lack standardization and external validation for C. auris specifically 3

Clinical Considerations

Diagnostic Challenges

• Blood cultures may be negative in cases of:
  • Extremely low-level candidemia
  • Intermittent candidemia
  • Deep-seated candidiasis after bloodstream clearance
  • Direct tissue inoculation without bloodstream involvement 1
• Antifungal therapy may compromise blood culture sensitivity, though specialized blood culture media (BacT/Alert FA PLUS or Bactec Plus Aerobic/F bottles) can effectively recover C. auris even in the presence of antifungal agents 4

Infection Control Implications

• Rapid and accurate identification of C. auris is critical due to:
  • High mortality rates (up to 64%) 5
  • Multidrug resistance patterns (only 10.7% susceptible to fluconazole) 5
  • Potential for healthcare facility outbreaks 6
• Close contacts of confirmed cases should be screened for C. auris colonization 2
• Environmental cleaning requires sporicidal disinfectants as quaternary ammonium compounds have poor activity against Candida species 2

Treatment Considerations

• Echinocandins are strongly recommended as first-line therapy for C. auris infections (90-98.2% susceptibility) 5
• Fluconazole should be avoided due to extensive resistance (only 10.7% susceptibility) 5
• Treatment should continue for at least 14 days after documented clearance of Candida from the bloodstream 5

While blood cultures remain essential for diagnosis, their limitations necessitate complementary diagnostic approaches for effective C. auris detection and management.