Purpose: To investigate the diagnostic accuracy of matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) in the identification of clinical oral Candida isolates.
Methods: In the first experiment, 170 suspected oral candidiasis patients were included. Unstimulated saliva was collected and cultured on solid plate (Sabouraud's agar) for 48 hours. Clinical isolates were analyzed by both PCR, which was used as golden standard, and MALDI-TOF MS. The diagnostic accuracy of MALDI-TOF MS for both C.albicans and non-C.albicans were investigated. In the second experiment, we tried to identify Candida isolates directly from positive liquid culture in a new cohort of 42 patients. MALDI-TOF MS identification of candida isolates were performed on positive liquid medium cultures directly. The data were analyzed using SPSS 18.0 software package.
Results: Totally, 230 clinical Candida isolates were isolated from 212 oral candidiasis patients enrolled. Out of the 230 analyzed clinical isolates, C. albicans (65.65%, 151/230) was the most frequently isolated species, followed by C. glabrata (11.74%, 27/230), and other candida species. The sensitivity and specificity of MALDI-TOF in identification of C. albicans were 93.33% and 92.73% respectively, and those for non-C. albicans were 83.64% and 89.2% respectively. Oral rinse followed by culturing in Sabouraud's liquid medium for 24 hours yield the diagnostic accuracy of 78.42% in MALDI-TOF MS identification.
Conclusions: C. albicans is the most frequent Candida spp. in oral candidiasis. MALDI-TOF MS is an effective and rapid method for identification of Candida spp. The on-plate based method generate much higher diagnostic accuracy than liquid culture based one.