Application of matrix-assisted laser desorption/ionizationtime-of-flight mass spectrometry system in identification of pathogenic bacteria

  Objective  To explore the value of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in the rapid identification of pathogenic bacteria in bloodstream infections, and to analyze the accuracy of MALDI-TOF MS method.

  Methods  Blood samples from 321 patients with bloodstream infection were collected for blood culture, and the results of bacterial culture in microbiology laboratory were all positive. Pathogenic bacteria was taken from the positive blood culture flask and placed into a separate gel tube, and MALDI-TOF MS was used to identify the enriched bacteria; at the same time, the samples were routinely cultured, and the pure colonies obtained were detected by VITEK 2 COMPACT microbial analysis system, and the identification results of the two methods were compared. If there were differences in the test results, further gene sequencing method would be carried out to determine.

  Results  Among 321 specimens for blood culture, 180 strains of Gram-negative bacilli were isolated, the identification accuracy rate of MALDI-TOF MS was 97.78%, no identification errors occurred and 4 strains were not identified. Among 141 strains of Gram-positive bacteria isolated, the Gram-positive coccus accounted for the most, and the identification accuracy rate of MALDI-TOF MS was 84.39%. One strain of Bacillus cereus was mistakenly identified as Escherichia coli, and there was an error in the identification of the genus level; the remaining was identified incorrectly at the level of the species.

  Conclusion  Compared with traditional blood culture and biochemical identification methods, MALDI-TOF MS method has a higher accordance rate in bloodstream infection, and the method is simple and rapid.