Rapid Identification of Candida Species in Candidemia Directly from Blood Samples Using Imperfect Match Probes

Abstract

Candidemia is associated with a high mortality rate, and initial adequate antifungal therapy results in a significant decrease in the crude mortality. We herein report a rapid method that can identify eight Candida species in candidemia using imperfect match quenching probes (IM Q-probes) within three and a half hours of whole blood sample collection. Furthermore, employing the D value, which reflects the difference between the Tm signature from a clinical isolate and that registered in the database, it is possible to quickly identify samples suitable for IM Q-probe identification. We first evaluated the method using 34 Candida colonies collected from different patients, and 100% (34/34) of the identification results matched the preidentified Candida species. We then performed blind tests using eight whole blood samples artificially mixed with eight different Candida species respectively, and all identification results correctly matched the preidentified Candida species. Finally, using 16 whole blood samples collected from candidemia patients, we compared the IM Q-probe method with the culture/sequencing method. Of a total of 16 patient samples, 100% (16/16) matched the culture and sequencing results. The IM Q-probe method is expected to contribute not only to the life expectancy of candidemia patients but also to antifungal stewardship.