Fast-tracking fungal detection: a rapid flow cytometric method for the detection of yeasts in blood cultures

Invasive fungal diseases (IFDs), such as candidemia are increasing in prevalence globally and impose greater risk of life-threatening infection for immunocompromised and hospitalized patients if not treated with appropriate antifungals. The “gold-standard” method for candidemia detection is culture based with low sensitivity, often taking days to obtain results. We have developed a novel flow-cytometric method that detects yeast cells in blood cultures using two fluorescent markers, providing results in just over 1 h. In our study, we investigated the performance of the markers in clinical isolates across 6 different yeast species in spiked blood cultures. Using flow-cytometry and confocal microscopy we investigated the staining specificity of the markers to non-yeast cells (i.e., human cells and bacteria) and validated our gating strategy using imaging cytometry. Our limit of detection using conventional flow cytometry was 2.871 × 10 3 cells/mL in spiked cultures and we successfully applied our assay to yeast positive clinical blood cultures, with the ability to detect unusual species such as Saccharomyces cerevisae . Compared to conventional microscopy, our assay demonstrates a superior LOD and with further optimization, could detect candidemia earlier to potentially improve patient outcomes.