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We always obtained at least one correct identification for the four trimicrobial samples, where five bacteria were identified with scores >1.7, except for one with a score of 1.675 (Table?2). No reliable identification was obtained for a bimicrobial sample and the single quadrimicrobial sample. All Stenotrophomonas maltophilia strains that were found only in polymicrobial samples remained unidentified. Finally, MALDI BioTyper identified 18 bacteria, 8/25 Gram-negative and 10/25 Gram-positive, respectively, according to the rules established in this study. Overall, MS succeeded in identifying 89.66% (477/532) of the bacteria identified by conventional procedures, contained in 503 BC samples. Even though BC is considered to be the reference standard for the detection of microorganisms in blood samples [2], it remains dependent on different factors, such as bacterial density [18], bacterial adaptation to new check details growth environments, this website individual rates of growth, competition between bacteria, and initial antimicrobial therapy. The delay in identification mostly remains unsatisfactory for clinicians, who often initiate presumptive antimicrobial therapy prior to precise diagnosis. Shortening the delay in providing dedicated therapy may strengthen its specificity, and would have a beneficial effect on the recovery of patients [3]. Because of the high sensitivity of MS in detecting peptides and the possibility of identifying bacteria with software such as Biotyper, it has been possible to demonstrate the high quality of identification [12]. Here, we propose a new protocol and rules for the identification of bacteria from BCs with MALDI-TOF BioTyper, which allowed 89.66% correct and single-step identifications among a total of 532 microorganisms from 503 blood samples, including polymicrobial samples from small volume of BC. Monomicrobial samples were correctly identified Tryptophan synthase at the species level in 95.22% of cases. All bacteria were identified within the 2�C3?h following BC positivity. The largest series consisted of 16 daily consecutive samples. Using a Vacutainer tube containing 1?mL of separation gel and two low-speed centrifugations from no more than 1.5?mL of BC, we observed better separation of bacteria from blood cells and more accurate bacterial identification than is possible with some published procedures which makes it difficult applying these to paediatric blood cultures [16,19,20]. In such an approach, a low level of bacteria and contamination by blood components may alter the stereotypes of bacterial protein spectra, and full adhesion of gel to tube walls is obligatory for good separation and recovery of bacteria. Protein extraction remains obligatory. Some authors have attempted more direct protein extraction, even from low volumes of BC, but have mainly obtained lower correct identification rates at the species level [11,15,21], or have needed more time, e.g.