🧫 Misidentification of Candida auris by Automated Systems – 2025 Update

Published: July 2025 | By: FRCPathPrep.com Editorial Team

Essential update for FRCPath Medical Microbiology Part 2 candidates and practicing microbiologists

🔍 Overview

Candida auris is a multidrug-resistant emerging fungal pathogen with high transmission potential in healthcare settings. Unlike other Candida spp., C. auris has the ability to cause persistent colonisation, survive on surfaces for extended periods, and resist multiple antifungal classes.

Despite its clinical importance, C. auris remains difficult to identify accurately using many commercial diagnostic platforms. Misidentification can lead to inappropriate treatment, failure to isolate, and rapid nosocomial transmission.

❗ Why It Matters

• C. auris can cause invasive candidiasis with high mortality (30–60%)

• Often misidentified as other yeasts — delaying diagnosis

• Frequently resistant to azoles, amphotericin B, and sometimes echinocandins

• Requires reference lab confirmation in many settings

• Mandatory notification and strict infection control are essential in the UK

⚠️ Common Misidentifications by Automated Systems

Here is a summary of how commonly used commercial identification systems may misidentify C. auris, especially if database libraries are outdated:

System	Common Misidentifications
VITEK 2 YST	Candida haemulonii, Candida duobushaemulonii
API 20C AUX	Rhodotorula glutinis (despite absence of red pigmentation), Candida sake
API ID 32C	Candida intermedia, Candida sake, Saccharomyces kluyveri
BD Phoenix Yeast ID	Candida haemulonii, Candida catenulata
MicroScan	Candida famata, Candida guilliermondii, Candida lusitaniae, Candida parapsilosis
RapID Yeast Plus	Candida parapsilosis

🔬 FRCPath Tip: If a Candida isolate shows resistance to fluconazole and is identified as a rare or unusual species, always consider C. auris — especially in ICU or outbreak settings.

🧪 Confirmatory Identification Methods

Method	Reliability for C. auris	Notes
MALDI-TOF MS	High — if database updated	Both Bruker and VITEK MS now include C. auris libraries
PCR / Real-time PCR	Very high	Available at reference labs
ITS sequencing	Gold standard	Not routinely available in all labs

🏥 Clinical Clues That Should Raise Suspicion

Scenario	Why It Matters
ICU or ventilated patient	High-risk population
Azole-resistant Candida from sterile site	Strong indicator
Repeated misidentification from same ward	Suggests outbreak
Yeast isolate with unusual profile	May be misidentified C. auris
Patient transferred from known outbreak area	Global risk (e.g., India, US, South Africa)

🔐 UKHSA Guidance (2025 Update)

UKHSA recommends the following actions if Candida auris is suspected:

1. Send isolates to the UKHSA Mycology Reference Laboratory for confirmation

2. Use MALDI-TOF if in-house and validated for C. auris

3. Initiate isolation precautions immediately

4. Screen contacts and the environment

5. Inform local Infection Control and Public Health Teams

💊 Antifungal Resistance Patterns

Antifungal	Typical Resistance in C. auris
Fluconazole	>90% resistant
Amphotericin B	30–50% resistant
Echinocandins	Generally susceptible; resistance emerging
Flucytosine	Variable, not typically used

🧠 First-line treatment: Echinocandin (e.g., anidulafungin, caspofungin)❗ Monitor closely and refer to reference AST results; consider combination therapy in refractory or pan-resistant cases.

🧼 Infection Control Measures (UKHSA)

Action	When to Implement
Single-room isolation	Immediately if suspected
Chlorhexidine washes	Daily for colonised patients
Contact screening	Patients sharing healthcare environment
Terminal cleaning	Sodium hypochlorite or HPV (hydrogen peroxide vapour)
Environmental cultures	If outbreak suspected

📚 FRCPath Part 2 Exam Tips

• Memorise key misidentification patterns (e.g., C. haemulonii → suspect auris)

• Know when to escalate to reference lab

• Be able to write a public health and infection control response in exam cases

• Revise UKHSA C. auris guidance (2025) and international updates

🔗 References

• UKHSA (2025). Candida auris: Laboratory Testing and Management in England

• CDC (2024). C. auris Clinical Alert and Lab Guidance

• EUCAST (2025). Antifungal MIC Distributions

• Public Health England (Archived): C. auris Outbreak Management Toolkit

🧠 Final Thought

Candida auris poses a diagnostic and infection control challenge. Misidentification can be costly — not just for the patient, but for entire healthcare systems. FRCPath candidates and practicing microbiologists alike must be proactive in recognising, confirming, and reporting potential C. auris cases.

🎓 Want more high-yield fungal infection updates and OSPE-style questions?

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