Rapid identification of Gram-negative organisms from blood culture bottles using a modified extraction method and MALDI-TOF mass spectrometry.

The application of matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry (MS) directly to blood culture broth has potential to identify bloodstream infection earlier and facilitate timely management. We prospectively tested a novel, rapid, and inexpensive in-house spin-lysis protocol with formic acid extraction and compared MALDI-TOF MS identification of Gram-negative bacteria with traditional phenotypic methods (Phoenix™) directly from 318 BACTEC™ (Becton Dickinson, Franklin Lakes, USA) blood cultures. The MS score was ≥1.7 in 268 (91.8%) monomicrobial broths, with concordance to genus and species level of 100% and 97.0%, respectively. MALDI-TOF MS still has limited capacity to detect all species in polymicrobial broths.