Surface-enhanced Raman spectroscopy (SERS) for the characterization of supernatants of bacterial cultures of bacterial strains causing sinusitis

Background: Sinusitis is defined as inflammation of the paranasal sinus mucous membrane lining caused by bacteria which usually invade the sinus by upper respiratory tract viral infections (UTI). Objectives: In the present study, Surface-enhanced Raman spectroscopy (SERS) has been applied to differentiate and characterize supernatant samples, in triplicate, of three different types of bacteria which are considered leading cause of sinusitis disease. Methods: For this purpose, supernatant samples of three different strains of bacteria namely Staphylococcus aureus, Klebsiella pneumoniae and Enterococcus faecalis. The SERS has identified significant changes as a result of secretions of biomolecules by these bacteria in their supernatants which can be helpful to explore the potential of this technique for the identification and characterization of different strains of bacteria causing same disease. Results: These differentiating characteristic SERS spectral features including 552 cm⁻¹ (C–S–S–C bonds), 951 cm⁻¹ (C[sbnd]N stretching), 1008 cm⁻¹ (Phenylalanine), 1032 cm⁻¹ (In plane C[sbnd]H bending mode Phenylalanine), 1280 cm⁻¹, 1320 cm⁻¹, 1329 cm⁻¹ (Amide III band), 1368 cm⁻¹, 1400 cm⁻¹, 1420 cm⁻¹ (COO⁻ sym. stretching and C[sbnd]H bending), 1583 cm⁻¹ (Tyrosine) correspond to Proteins and 1051 cm⁻¹ (C–C, C–O, –C–OH def.) correspond to carbohydrates contents of these three different types of bacterial secretions in their respective supernatants. Furthermore, multivariate data analysis techniques like principal component analysis (PCA) and a supervised method partial least squares-discriminant analysis (PLS-DA) were found to be useful for the identification and characterization of different bacterial supernatants. Conclusions: Surface-enhanced Raman spectroscopy is proven to be a helpful approach for the characterization and discrimination of three bacterial supernatants including S. aureus, K. pneumonia and E. faecalis.