Direct identification of bacteria from positive BacT/ALERT blood culture bottles using matrix-assisted laser desorption ionization–time-of-flight mass spectrometry

• We establish a low-cost method for identification of bacteria from blood bottles.
• The method is quick, providing results in less than 20 minutes per sample.
• Identification rates are high compared to most methods found in the literature.
• Significant time savings could impact clinical management of antibiotic treatment.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry is a fast and robust method for the identification of bacteria. In this study, we evaluate the performance of a laboratory-developed lysis method (LDT) for the rapid identification of bacteria from positive BacT/ALERT blood culture bottles. Of the 168 positive bottles tested, 159 were monomicrobial, the majority of which were Gram-positive organisms (61.0% versus 39.0%). Using a cut-off score of ≥1.7, 80.4% of the organisms were correctly identified to the species level, and the identification rate of Gram-negative organisms (90.3%) was found to be significantly greater than that of Gram-positive organisms (78.4%). The simplicity and cost-effectiveness of the LDT enable it to be fully integrated into the routine workflow of the clinical microbiology laboratory, allowing for rapid identification of Gram-positive and Gram-negative bacteria within an hour of blood culture positivity.