Performance of the matrix-assisted laser desorption ionization time-of-flight mass spectrometry system for rapid identification of streptococci: a review

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been developed as a new type of soft ionization mass spectrometry in recent years. An increasing number of clinical microbiological laboratories consider it as an innovative approach for bacterial identification. This study was undertaken in order to evaluate the use of MALDI-TOF MS for rapid identification of the clinical streptococci. A systematic review was conducted based on a literature search of the Medline and Embase databases. Fixed-effects models based on the P-value and the I-square were used for meta-analysis while considering the possibility of heterogeneity between studies. Statistical analyses were performed by using STATA 11.0. Twenty-seven studies covering 3,540 streptococci were included in our meta-analysis. The MALDI-TOF MS correctly identified the species of 96% (I-2 = 92.8, P < 0.1) of the streptococci. The MALDI-TOF MS correctly identified the species of 99% of the Streptococcus pneumoniae (I-2 = 85.2%, P < 0.1), 100% of the Streptococcus pyogenes (I-2 = 32.8%, P > 0.1), and 100% of Streptococcus agalactiae (I-2 = 20.7%, P > 0.2). What's more, it also had high confidence in other Streptococcus. But the accuracy of bovis needs to be improved. The overall performance of both MALDI-MS systems was different. Notably, the identifying accuracy rate of streptococci by VITEK MS was 98%, compared to 94% by the MALDI biotyper system. Interestingly, when analyzing the incorrect identification of MALDI-TOF MS, 36 out of the 38 strains of Streptococcus mitis/oralis were inaccurately identified as Streptococcus pneumoniae by the MALDI biotyper system. In conclusion, the results of this review indicated that MALDI-TOF MS could be a reliable and rapid method for identification of the streptococci.