Barcoding bacterial cells: a SERS‐based methodology for pathogen identification

Abstract

A principal component analysis (PCA) based on the sign of the second derivative of the surface-enhanced Raman scattering (SERS) spectrum obtained on in situ grown Au-cluster-covered SiO 2 substrates results in improved reproducibility and enhanced specificity for bacterial diagnostics. The barcode-generated clustering results are systematically compared with those obtained from the corresponding spectral intensities, first derivatives and second derivatives for the SERS spectra of closely related cereus group Bacillus strains. PCA plots and the corresponding hierarchical cluster analysis (HCA) dendrograms illustrate the improved bacterial identification resulting from the barcode spectral data reduction. Supervised discriminant function analysis (DFA) plots result in slightly improved group separation but show more susceptibility to false positive classifications than the corresponding PCA contours. In addition, this PCA treatment is used to highlight the enhanced bacterial species specificity observed for SERS as compared to normal bulk (non-SERS) Raman spectra. The identification algorithm described here is critical for the development of SERS microscopy as a rapid, reagentless and portable diagnostic of bacterial pathogens.

Raman spectroscopy: techniques and applications in the life sciences

“…Bacteria discrimination was first shown with Ag colloid SERS, showing discrimination at the strain level for E. Coli [319]. Differences in SERS spectra of various other bacteria species was also shown shortly after [320], and was shown to be potentially useful for bacteria 'barcoding' using multivariate statistics [321]. Different Ag NPs used for SERS were investigated for their antibacterial activity, and it was found that smaller (18 nm) were more toxic to bacteria than 80nm [322].…”

Plataformas nanoestructuradas de plata para identificación cualitativa de Escherichia coli mediante espectroscopia Raman intensificada por efecto de superficie “prueba de concepto del sistema”

“…Posteriormente, producto de la presencia de las bacterias y su interacción con el láser incidente, los pilares se alinean entre sí creando de este modo hot spots (zonas de aumento de campo electromagnético) que incrementan la intensidad de la señal Raman. Este mismo efecto ha sido utilizado para explicar el efecto SERS en otros estudios, utilizando sustratos diferentes [3,7,[16][17][18][19].…”

Surface-Enhanced Raman Scattering as an Emerging Characterization and Detection Technique

“…The identification and classification of bacteria causing urinary tract infections were demonstrated by Goodacre group using citrate reduced AgNPs [123]. The use of gold-coated silica nanoparticles as substrate and a barcoding approach was later used for the bacterial identification by Zeigler group [144]. The major problem with the application of SERS as a technique for microorganism identification is the spectral reproducibility.…”