Evaluation of Rapid Sepsityper® protocol and specific MBT-Sepsityper module (Bruker Daltonics) for the rapid diagnosis of bacteremia and fungemia by MALDI-TOF-MS

Abstract

During bloodstream infections, rapid adaptation of empirical treatment according to the microorganism identified is essential to decrease mortality. The aim of the present study was to assess the microbiological performances of a new rapid version of the Sepsityper® kit (Bruker Daltonics) allowing identification of bacteria and yeast by MALDI-TOF mass spectrometry directly from positive blood cultures in 10 min and of the specific MBT-Sepsityper module for spectra analysis, designed to increase identification performance. Identification rates were determined prospectively on 350 bacterial and 29 fungal positive blood cultures, and compared to conventional diagnostic method. Our rapid diagnosis strategy (Rapid Sepsityper® protocol: one spot with and one without formic acid extraction step) combined to MBT-Sepsityper module provided 65.4%, 78.9% and 62% reliable identification to the species level of monomicrobial positive blood cultures growing respectively Gram-positive, Gram-negative bacteria or yeast. Importantly, identification rates of Gram-positive bacteria were higher in anaerobic than in aerobic bottles (77.8% vs 22.2%; p = 0.004), if formic acid extraction step was performed (60.8% vs 39.2%; p = 1.8e−6) and if specific MBT-Sepsityper module was used (76.2% vs 61.9%, p = 0.041) while no significant differences were observed for Gram-negative bacteria. For yeasts identification, formic acid extraction step improved rapid identification rate by 37.9% while the specific MBT-Sepsityper module increased overall performances by 38%, providing up to 89.7% reliable identification if associated with the standard Sepsityper® protocol. These performances, associated with a reduce turnaround time, may help to implement a rapid identification strategy of bloodstream infections in the routine workflow of microbiology laboratories.