Surface-enhanced Raman spectroscopy (SERS) for monitoring colistin-resistant and susceptible E. coli strains.

The emergence of drug-resistant bacteria is a precarious global health concern. In this study, surface-enhanced Raman spectroscopy (SERS) is used to characterize colistin-resistant and susceptible E. coli strains based on their distinguished SERS spectral features for the development of rapid and cost-effective detection and differentiation methods. For this purpose, three colistin-resistant and three colistin susceptible E. coli strains were analyzed by comparing their SERS spectral signatures. Moreover, multivariate data analysis techniques including Principal component analysis (PCA) and Partial Least Squares-Discriminant Analysis (PLS-DA) were used to examine the SERS spectral data of colistin-resistant and susceptible strains. PCA technique was employed for differentiating colistin susceptible and resistant E.coli strains due to alteration in biochemical compositions of the bacterial cell. PLS-DA is employed on SERS spectral data sets for discrimination of these resistant and susceptible E. coli strains with 100% specificity, 100% accuracy, 99.8% sensitivity, and 86% area under receiver operating characteristics (AUROC) curve.

Surface-enhanced Raman spectral investigation of antibacterial activity of zinc 3-chlorobenzoic acid complexes against Gram-positive and Gram-negative bacteria.

BACKGROUND: Raman spectroscopy is an effective tool for determining the antibacterial actitivites of organometallic compounds against different bacterial strains. OBJECTIVES: The purpose of current study is to check the anibacterial activites of ligand (3-chlorobenzoic acid) and its respective zinc complex against gram positive and gram-negative bacterial strains by using surface enhanced Raman spectroscopy (SERS). METHODS: The ligand (3-chlorobenzoic acid) and its respective zinc complex caused different biochemical changes in gram-positive and gram-negative bacterial strains such as lipid contents, DNA/RNA contents, proteins contents, peptidoglycan contents and bacterial spore contents which can be observed with different SERS spectral features. Furthermore, PCA was employed for differentiating the mechanism of action of zinc complexes against gram-positive bacterial strain and gram-negative bacterial strain. RESULTS: Surface enhanced Raman spectroscopy (SERS) has been employed for analyzing the antibiotic activities of 3-chlorobenzoic acid ligands and their respective zinc complexes against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive) bacterial strains. The bioactivity assay and SERS spectral results clearly show that the complex causes more degradation in both bacterial cells (E. coli and B. subtilis) as compared to ligand. Furthermore, PCA was employed for differentiating the mechanism of action of zinc complexes against gram-positive bacterial strain and gram-negative bacterial strain. CONCLUSION: SERS technique along with chemometric tools have successfully differentiated the antibiotic activities of 3-chlorobenzoic acid ligands and their respective zinc complexes against Escherichia coli (gram-negative) and Bacillus subtilis (gram-positive) bacterial strains.