Проблемы особо опасных инфекций (Dec 2017)
Mass Spectrometric Analysis of Natural and Antigen-Modified Strains of Tularemia Agent
Abstract
Objective. Comparative study of the protein profiles of typical virulent strains and their isogenic avirulent LPS-defective mutants of Francisella tularensis using mass spectrometric analysis. Materials and methods. Six typical virulent strains of F. tularensis of three main subspecies and eight isogenic avirulent variants which have different lesions in LPS structure were used in this investigation.Protein spectra were obtained by MALDI-TOF MS using mass spectrometer Autoflex speed III Bruker Daltonics and Flex Control software of Biotyper. Earlier we expanded the database by introduction of the mass spectra of 40 typical F. tularensis strains of the three main subspecies. Results and conclusions. It was shown that the high quality spectrograms were obtained by means of the extraction of bacteria with ethanol supplemented with formic acid, as compared with two other methods (extraction matrix or TFA).According to the data received, the typical virulent strains of tularemia agent of the three main subspecies have significant differences in the major peaks of protein profiles. This suggests that MALDI-TOF MS can be used for the subspecies differentiation of F. tularensis.However, a comparative study of the protein spectra of virulent and isogenic avirulent F. tularensis strains of the same subspecies did not detect any essential differences. We were able to identify only two individual peaks (m/z 4673, 6929) which were characteristic of all virulent strains and one peak (m/z 7256) – of all avirulent strains. Thus, MALDI-TOF MS allows for reliable determination of the subspecies affiliation of F. tularensis strains but does not allow for evaluation of the strains` virulence. The results indicate that MALDI-TOF MS is a useful method for identification of typical and antigen-modified LPS-defective F. tularensis strains.
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