Evaluation of an optimized method to directly identify bacteria from positive blood cultures using MALDI‐TOF mass spectrometry

BACKGROUND: Although various methods have been developed to directly identify bacteria from positive blood cultures by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS), the necessity of using commercial kits still leads to a high cost and long assay time. Moreover, few evaluations of these methods have been conducted. This study aimed to evaluate the feasibility of an optimized MALDI‐TOF MS method for direct identification of bacteria in positive blood cultures. METHODS: A total of 829 non‐repeated positive cultures were collected from July 2018 to August 2019, and direct identification was performed by an optimized MALDI‐TOF MS method. The same positive blood cultures were sub‐cultivated to obtain a single bacterial colony and identified by classical biochemical BD testing, which is the gold standard to compare the accuracy of direct identification of positive blood cultures by MALDI‐TOF MS. RESULTS: After excluding 7 false‐positive samples from the 829 positive blood cultures, the most accurate rate of direct identification by this optimized MALDI‐TOF MS method was for gram‐negative bacteria (91.5%), followed by gram‐positive bacteria (88.3%), fungi (84.8%), anaerobic bacteria (80%), and other rare bacteria (66.67%). CONCLUSION: Common bacteria in positive blood cultures can be identified directly within 1 hour by MALDI‐TOF MS, and thus, this optimized method can be used as a primary identification method by clinicians. Routine implementation of this method may significantly increase the optimal utilization rate of antibiotics and decrease mortality in bacteremia patients.