Fast differentiation of bacteria causing pharyngitis by low resolution Raman spectroscopy and PLS-discriminant analysis

The diagnosis of the bacteria that cause pharyngitis through classical microbiological methods is a difficult, but usually very efficient task. However, the high cost of reagents and the time required for such identifications, about four days, could generate serious consequences, mainly when the patients concerned are children, the elderly or adults with low resistance. Thus, the search for new methods allowing a fast and reagentless differentiation of these microorganisms is extremely relevant. In this work, the main microorganisms responsible for pharyngitis, S. aureus, S. pyogenes and N. gonorrhoeae were studied. For each microorganism, sixty different dispersions were prepared using physiological solution as solvent. The Raman Spectra of these dispersions were recorded using a diode laser operating in the near infrared region. The PLS-discriminant analysis method was applied to bacteria differentiation through their respective Raman Spectra. This approach enabled the correct classification of 100% of all evaluated bacteria and unknown samples coming from clinical environment, in a reduced time interval (ca. 10 h), by using a low-cost, portable Raman spectrometer, which can be easily used in Intensive Care Units (ICU) and clinical environments.