[Performance of two matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) models for identification of bacteria isolated from blood culture].

We compared the results of two bacterial identification methods: 1) a traditional method based on phenotypic identification of the causative organism using gram-staining, culture and biochemical markers and 2) matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). A total of 111 isolates, including 107 strains of common bacteria species and 4 strains of 3 yeast species, were tested by the traditional method and MALDI-TOF MS method(VITEK MS and Micro flex LT). Data obtained using MALDI-TOF MS were classified as Level 1 and Level 2 according to the confidence level of identification results from the VITEK MS ver. 1.0 database (VITEK MS) and MALDI Biotyper ver. 2.0 database (Microflex LT). The proportions of measured samples identified as Level 1 were 98.2% with the VITEK MS database and 87.4% with the MALDI Biotyper database. The concordance rates of the traditional method were 93.7% with the VITEK MS database and 82.0% with the MALDI Biotyper database. Identification results of five strains were mismatched between the traditional method and MALDI-TOF MS. Their ribosomal RNA sequences were identical to the results obtained from MALDI-TOF MS. We concluded that the performance of VITEK MS is superior to that of the traditional method and Microflex LT.