Matrix-assisted laser desorption ionization–time of flight mass spectrometry as an alternative to 16S rRNA gene sequencing for identification of difficult-to-identify bacterial strains

An ammonium chloride erythrocyte-lysing procedure was used to prepare a bacterial pellet from positive blood cultures for direct matrix-assisted laser desorption–ionization time of flight (MALDI-TOF) mass spec-trometry analysis. Identification was obtained for 78.7 % of the pellets tested. Moreover, 99 % of the MALDI-TOF identifications were congruent at the species level when considering valid scores. This fast and accurate method is promising. Blood cultures are the best approach to establishing the etiology of bloodstream infections and infectious endocarditis. Moreover, rapid identification of the etiological agents of such severe infections is pivotal to guiding antimicrobial therapy. Thus, the impact of timely microbiology laboratory reporting is maximal at the notification of positive blood cultures (5). Ma-trix-assisted laser desorption–ionization time of flight mass spectrometry (MALDI-TOF MS) allows identification of both gram-positive (2, 7) and gram-negative bacteria (1, 4) to the species level in a few minutes by measuring the molecula