Rapid, Label-Free Prediction of Antibiotic Resistance in Salmonella typhimurium by Surface-Enhanced Raman Spectroscopy.

The rapid identification of bacterial antibiotic susceptibility is pivotal to the rational administration of antibacterial drugs. In this study, cefotaxime (CTX)-derived resistance in Salmonella typhimurium (abbr. CTXr-S. typhimurium) during 3 months of exposure was rapidly recorded using a portable Raman spectrometer. The molecular changes that occurred in the drug-resistant strains were sensitively monitored in whole cells by label-free surface-enhanced Raman scattering (SERS). Various degrees of resistant strains could be accurately discriminated by applying multivariate statistical analyses to bacterial SERS profiles. Minimum inhibitory concentration (MIC) values showed a positive linear correlation with the relative Raman intensities of I990/I1348, and the R2 reached 0.9962. The SERS results were consistent with the data obtained by MIC assays, mutant prevention concentration (MPC) determinations, and Kirby-Bauer antibiotic susceptibility tests (K-B tests). This preliminary proof-of-concept study indicates the high potential of the SERS method to supplement the time-consuming conventional method and help alleviate the challenges of antibiotic resistance in clinical therapy.

Rapid Identification of Mixed Enteropathogenic Bacteria by Means of Au Nanoparticles@Bacteria Using Portable Raman Spectrometer.

Rapid detection of food-borne pathogens is the most critical and urgent issue among all the current food safety problems. As enhanced substrate, nanoparticles are widely used in surface enhanced Raman scattering (SERS) because of unique optical and physicochemical properties. In this study, Au nanoparticles with monodisperse and good reproducibility were synthesized by using sodium citrate reduction method. Applying Au nanoparticles sol as enhanced substrate, a portable Raman spectrometer had been applied for rapid detection of single and mixture pathogenic bacterial contamination by SERS. The results indicated that Escherichia coli, Salmonella typhimirium, Shigella flexner and Staphylococcus aureus showed specific Raman phenotypes at 600∼1700 cm-1. Generally, different bacteria could be easily and instantly recognized by its Raman phenotypes. The PC-LDA classification model was set up by combined bacterial Raman phenotypes with the multivariate statistical analysis. With the short-time inoculation, four enteropathogenic bacteria could be rapidly, precisely, sensitively and specifically identified. Furthermore, the model also had a good ability to predict the mixed contamination. This research provides the possibility of rapid detection in the food and biomedical fields.

Metabolism of benzo[a]pyrene in peroxynitrite/Fe(III) porphyrin system.

The peroxynitrite/porphyrin biomimetic system was established to investigate the effects of peroxynitrite on benzo[a]pyrene (B[a]P) metabolism. Three model systems consisting of different iron porphyrins were compared, and the results showed that the peroxynitrite/T(p-Cl)PPFeCl system was the highest catalytic efficiency in the metabolism of B[a]P. We analyzed the B[a]P metabolites produced from this system by RP-HPLC method and firstly identified the formation of nitrobenzo[a]pyrenes which are the special metabolites of B[a]P induced by peroxynitrite.