Rapid identification of Candida sp. by MALDI‐TOF mass spectrometry subsequent to short‐term incubation on a solid medium

Rapid identification of Candida species is important for appropriate antifungal therapy of fungemia. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) system is a useful tool to identify bacteria and yeasts. In this study, we evaluated the feasibility of identifying yeasts after a short‐term incubation on a solid medium. We tested 24 strains of eight Candida species. Blood culture bottles were spiked with a calibrated suspension of each Candida strain. Three different culture media, two types of blood culture bottles and three different incubation time points were tested. A multivariable random‐effects logistic regression analysis was performed for determining factors independently associated with a successful MALDI‐TOF MS identification. One‐hundred and thirty‐one out of 432 MALDI‐TOF MS analyses (30%) exhibited a score ≥ 1.7. The performance of the technique varied across Candida species. Factors associated with a successful identification were the use of a chromogenic Candida medium and the time points 4 and 5 h. Using the factors ‘chromogenic Candida medium’ and time point 5 h the global performance of identification reached 60% and a mean MALDI‐TOF score of 1.78. Identifying yeasts after a short‐term incubation on a solid medium seems possible, especially when using a chromogenic Candida medium and respecting at least 5 h of incubation. This assay was a first step and needs to be completed using more strains, various chromogenic Candida medium and maybe also testing a longer culture time such as 6 h.