Anup K Ghosh*. Amit Rajbanshi, Joseph Jillwin, M R Shivaprakash and A Chakrabarti

Rapid identification of yeast pathogens from positive blood cultures by MALDI-TOF MS


Early detection and identification of yeast isolates from blood are important for treatment and management. Yeasts identification by conventional method takes time and may lead to delayed appropriate therapy. DNA sequencing technique, thorugh reliable, may be reasonably time consuming, expensive and need expertise. Matrix-assisted laser desorption/ionization - time of flight (MALDI-TOF) mass spectrometry has been proposed as a new method for the rapid identification of microorganisms. Atotal of300 clinical yeasts isolated from blood cultures were included in this study. 150 out of 300 Candida species were identified with conventional methods, molecular method by using ITS and 28S (D1/D2) region and ribosomal DNA as well as with MALDITOF-MS. The rest 150 blood isolates were identified directly by MALDI. The correlation of yeasts identification between molecular methods and MALDI-TOF was extremely high and can identify 97% to the species level and 100% to the genus level. Rare isolates like C. nivariensis, C. rugosa, C. pararugosa, C. catenulata and C metapsilosis were also identified by MALDI. Two isolates of Candida auris and one isolate of Blastobotrys adeninivorans could not be identified by MALDI due to non availability of the signature in the database. Blood yeasts identified directly by MALDI shows 98% identification to the species level where C. tropicalis was the maximum 41(27.3%) followed by C. pelliculosa33(22%), C. krusei 19(12.6%), C. glabrata 16(10.6%), C. albicans 13(8.6%), C. guillermondii 10(6.6%), and C. parapsilosis 8(5.3%). MALDI can even identified rare Candida spp. like C. orthopsilosis, Magnusiomyces capitatus and Pseudozyma aphidis isolated from the blood were also identified using MALDI TOF-MS. Identification of blood yeast by MALDI is reliable, fast and cost effective. This new approach could improve yeast diagnostics due to low turn-around time. This would help in optimal appropriate antifungal therapy. 9830;Corresponding author E-mail:[email protected]

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Society for Indian Human and Animal Mycologists 2014