Detection of molecular changes induced by antibiotics in Escherichia coli using vibrational spectroscopy.

This study aimed to test Raman (400-1800cm-1 ) and Infra-red (1900-500cm-1 ) spectroscopies followed by statistical analysis (principal component analysis) to detect molecular changes induced by antibiotics (ampicillin, cefotaxime - cell wall synthesis inhibitors, tetracycline - protein synthesis inhibitor, ciprofloxacin - DNA synthesis inhibitor) against Escherichia coli TOP10. In case of ampicillin and cefotaxime, a decrease in protein bands in both Raman (1240, 1660cm-1 ), and IR spectra (1230, 1530, 1630cm-1 ), and an increase in carbohydrate bands (1150, 1020cm-1 ) in IR spectra were observed. Tetracycline addition caused an increase in nucleic acid bands (775, 1478, 1578cm-1 ), a sharp decrease in phenylalanine (995cm-1 ) in Raman spectra and the amide I and amide II bands (1630, 1530cm-1 ) in IR spectra, an increase in DNA in both Raman (1083cm-1 ) and IR spectra (1080cm-1 ). Regarding ciprofloxacin, an increase in nucleic acids (775, 1478, 1578cm-1 ) in Raman spectra and in protein bands (1230, 1520, 1630cm-1 ), in DNA (1080cm-1 ) in IR spectra were detected. Clear discrimination of antibiotic-treated samples compared to the control was recorded, showing that Raman and IR spectroscopies, coupled to principal component analysis for data, could be used to detect molecular modifications in bacteria exposed to different classes of antibiotics. These findings contribute to the understanding of the mechanisms of action of antibiotics in bacteria.