What is the comparison between Polymerase Chain Reaction (PCR) and culture for Candida auris screening?

From the Guidelines

For screening Candida auris, PCR testing is generally preferred over culture methods due to its higher sensitivity and faster turnaround time. This recommendation is based on the most recent and highest quality study available, which highlights the importance of rapid detection and identification of C. auris in high-risk settings and during outbreaks 1. The study notes that molecular methods, such as PCR, can increase the rate of microbial detection in respiratory samples and provide a significantly shorter median turnaround time compared to conventional cultures.

Some key points to consider when implementing PCR testing for C. auris screening include:

• PCR can detect C. auris within hours, compared to cultures which may take several days
• PCR can identify the fungus even at low concentrations
• Culture methods remain important for antimicrobial susceptibility testing and for confirming PCR results
• The optimal approach often combines both methods: initial PCR screening followed by culture confirmation when positive
• Samples should be collected from axilla and groin for colonization screening, while clinical specimens depend on the suspected infection site

Healthcare facilities should establish clear protocols for when to use each method based on their specific needs, resources, and the prevalence of C. auris in their patient population 1. The higher cost of PCR should be weighed against its benefits in rapid detection and infection control. It is also important to note that C. auris is a critical and high-priority pathogen, and its detection and management require a comprehensive approach that includes surveillance, infection control, and antimicrobial stewardship 1.

From the Research

C. auris Screen Test: PCR vs Culture

• The choice between PCR and culture for C. auris screen testing depends on various factors, including sensitivity, specificity, and turnaround time 2.
• Culture-based methods are considered the gold standard for identifying C. auris, but they can be time-consuming and may not detect the organism in all cases 2.
• PCR-based methods, on the other hand, offer faster turnaround times and higher sensitivity, but may not provide information on antifungal susceptibility 2.
• A study comparing the efficacy of different antifungal agents against C. auris found that echinocandins, such as anidulafungin and caspofungin, showed lower MIC values than amphotericin B, but were not fungicidal at any concentration 3.
• Another study highlighted the importance of early and correct identification of patients colonized with C. auris in containing its spread, and discussed the challenges in sample collection, laboratory culture-dependent and independent identification, and susceptibility profile of C. auris 2.
• The activities of nine antifungal agents against C. auris biofilms were studied, and the results showed that triazoles, echinocandins, and liposomal amphotericin B appear to have less activity against C. auris biofilms than deoxycholate amphotericin B 4.
• Rezafungin, a novel echinocandin, was found to be effective in the treatment of disseminated C. auris infection using an immunocompromised mouse model, with significantly lower average log10 cfu/g of tissue compared with amphotericin B- and vehicle-treated mice 5.
• Understanding the mechanisms of echinocandin resistance in C. auris is crucial, and a study found that only isolates carrying mutations in FKS1 are echinocandin resistant, and that routine in vitro testing of C. auris isolates for susceptibility to caspofungin by the broth microdilution method should be viewed cautiously or avoided 6.