Spectral investigation of clinical isolates of S.pneumoniae, S.oralis and S.mitis by Raman spectroscopy

Abstract

Nowadays, various inflammatory diseases of the oral cavity, including periodontitis, have become widespread. In addition to the fact that periodontitis itself leads to tooth loss, disruption of the occlusal relationships of the jaws and chewing function, it is also an important risk factor for complications during dental implantation [1-2]. One of the known potential participants in the pathological process is streptococci, which are detected in periodontal pockets in almost 100% of cases [3-5].
4 strains of S.mitis, 4 strains of S.oralis and 3 strains of S.pneumoniae were used as research objects.
To exclude the contribution of autofluorescence, a modified method of subtracting the fluorescent component by polynomial approximation Improved Modified Multi-Polynomial Fitting (ExModPoly) with a polynomial degree of 8 was used. Raman spectra were analyzed in the range 450-1800 cm-1.
For additional analysis of the studied samples, the linear discriminant analysis method was used in the RS-tool program.
The main spectral differences are visible at 527 cm-1 (S-S disulfide stretching in proteins, Phosphatidylserine or ν(S-S) gauche-gauche-trans (aminoacid cysteine)), 621 cm-1 (C-C twisting mode of phenylalanine (proteins)), 1280 cm -1 (Amide III, CH2 wagging vibrations from glycine backbone or proline side chains), 1333 cm-1 (Guanine), 1445 cm-1 (CH2 bending modes, deformation C-H bending proteins, deformation CH2/CH3 in lipids), 1525 cm -1 (Amide II), 1692 cm-1 (Stretching CO), 1749 cm-1 (C=O, lipids). Also, criteria were introduced for identifying groups of samples based on the line intensities of the averaged Raman spectra and the discriminant analysis performed.

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Alena Zotova
Samara National Research University
Russia

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