Direct identification of yeasts from blood culture by MALDI-TOF mass spectrometry

Abstract

This study aimed to identify yeasts directly from positive blood cultures by MALDI-TOF mass spectrometry. This was a 5-month prospective study (February to June, 2015) carried out on bottles of blood cultures from in-patients at the Hôpital de l'ARCHET at the CHU, Nice. Positive blood culture broth was analysed by MALDI-TOF mass spectrometry using Sodium Dodecyl Sulphate (SDS) as the lysis buffer. Out of 64 samples, 51 (79.6%) were identified by MALDI-TOF mass spectrometry at the species level and 12 strains (18.7%) at the genus level. The isolated yeasts fell into six species: Candida albicans 37.2%, Candida glabrata 31.4%, Candida parapsilosis 15.7%, Candida tropicalis 5.9%, Candida krusei 5.9%, and Candida lusitaniae 3.9%. In comparison, 95.3% of species were identified from cultured colonies, the main ones being C. albicans (37.1%), C. glabrata (30.7%) and C. parapsilosis (16.1%). Identification of yeasts from blood culture bottles by MALDI-TOF mass spectrometry is a fast, reliable technique. However, analysis of colonies remains the best technique for identification and for antifungal imaging in order to refer the patient to the most appropriate therapy.