Species identification of enterobacteria strains by means of MALDI-TOF MS
The article presents results of MALDI-TOF mass spectrometry usage for identification of microorganisms of Proteus mirabilis, Yersinia enterocolitica, Enterobacter cloacae species, which were isolated in 2016 from pathological material and sanitary control facilities of livestock and poultry farms, unfavourable as far as gastrointestinal diseases were concerned. Primarily, species differentiation was carried out on the basis of studying tinctorial, cultural-morphological and biochemical properties. To study the proteomes of bacterial cultures, their MALDI-TOF profiling (analysis of protein profiles that are extracted from whole bacteria) was carried out and their compliance was confirmed. Prints of proteins with different molecular weights were obtained using a MALDI-TOF Microflex LT mass spectrometer (BrukerCorp., Billerica, USA) with detection in a linear positive mode at a laser frequency of 50 Hz and in the mass range from 2000 to 30,000 Da. The creep voltage was 20 kV, and the extraction dwell time was 200 ns. To generate each ion spectrum, at least 10 laser images per sample were used. For each bacterial sample, a total of 100 prints of proteins with different molecular weights were averaged and processed using the MALDI Biotyper software (BrukerCorp., Billerica, USA). Thus, in the studies it was established that the Prot2 strain belongs to Proteus mirabilis species, Ye3-Yersinia enterocolitica, En2-Enterobacter cloacae.