A Comparison of “Low-Molecular” and Conventional Approaches to the Species Identification of Bacteria by MALDI Mass Spectrometry

Resumo

A new approach to bacteria identification that uses the standard software for building mass spectral libraries of low-molecular compounds and for corresponding library searches is compared with the conventional approach based on the commercial Biotyper software and database. The results are obtained for a random sample of 100 mass spectra of 25 strains of S. pyogenes, S. dysgalactiae subsp. equisimilis, and S. anginosus. The spectra were sampled from the database of 728 mass spectra of 182 strains for some Streptococcus species. Both approaches were proved to result in the similar identification as 80–88% of the true outcomes. For similar reference mass spectra and the same identification criteria, the results of identification were very close to each other as 24 agreements for 25 strains. This is because different estimations of mass spectral similarity included in the programs under comparison lead to a correlation of similarity indicators. The difference in usual identification results is mainly due to different reference databases and also different identification criteria.