620. Development and Validation of a Novel qPCR Assay for Differentiation of Common Candida Pathogens including C. auris

BACKGROUND: Candida is a common asymptomatic fungal colonizer of humans. Of the 200+ total species in the genus Candida, only a few are known to cause infection. The most common are C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. krusei, and C. auris. In the USA, candidemia is the fourth most common cause of bloodstream infections in hospitalized patients. Although antifungal medication can treat candidemia, mortality rates remain between 30 and 60%. Eurofins Viracor has developed a qPCR assay that will qualitatively detect and differentiate any of the 6 previously listed Candida species in whole blood. Speciation is critical for treatment due to variable drug susceptibility among different species, particularly C. auris due to its multi-drug resistance. METHODS: Multiple primer/probe mixes were designed around and within the ITS1, 5.8s, ITS2, and 28s ribosomal subunit regions in each of the six Candida target species. The 5.8s and 28s regions are heavily conserved, while the ITS regions are highly divergent and used to differentiate species. After optimization, the six primer/probe mixes were partially multiplexed resulting in four mixes covering all species. DNA was extracted from human blood spiked with viable Candida using the MagMAX™ DNA Multi-Sample Ultra 2.0 Kit, and eluates were amplified using the Applied Biosystems™ 7500 Fast platform. RESULTS: Each assay met all validation acceptance criteria and demonstrated excellent accuracy, precision, linearity and dynamic range, and sensitivity. 32 non-Candida fungal and bacterial pathogens that commonly cause bloodstream infections were used to assess specificity. All specificity samples were negative for all Candida targets. To assess accuracy, 75 of 75 Candida samples representing all six species across a range of concentrations were tested and correctly identified. 24 of 25 known-negative samples were negative, with one positive C. glabrata C(T) result observed just below the cutoff. CONCLUSION: Traditional blood culture methods for Candida species identification can be too time consuming for a quickly progressing infection. The Candida qPCR assay described here not only detects an infection faster but provides accurate speciation allowing for rapid and targeted antifungal treatment options for the patient. DISCLOSURES: Clayton Thomas, BS in Biology, Eurofins Viracor: Employee James Grantham, n/a, Eurofins Viracor: Employee Emily Lute, n/a, Eurofins Viracor: Employee Jerod Davidson, n/a, Eurofins Viracor: Employee Scott Cowden, MS, MB ASCP(CM), Eurofins Viracor: Employee Jamie Nutt, n/a, Eurofins Viracor: Employee