Raman spectroscopic detection of physiology changes in plasmid-bearing Escherichia coli with and without antibiotic treatment

Abstract

Bacterial resistances against antibiotics are increasingly problematic for medical treatment of pathogenic bacteria, e.g., in hospitals. Resistances are, among other genes, often encoded on plasmids which can be transmitted between bacteria not only within one species, but also between different species, genera, and families. The plasmid pDrive is transformed into bacteria of the model strain Escherichia coli DH5α. Within this investigation, we applied micro-Raman spectroscopy with two different excitation wavelengths in combination with support vector machine (SVM) and linear discriminant analysis (LDA) to differentiate between bacterial cultures according to their cultural plasmid content. Recognition rates of about 92% and 90% are achieved by Raman excitation at 532 and 244 nm, respectively. The SVM loadings reveal that the pDrive transformed bacterial cultures exhibit a higher DNA content compared to the untransformed cultures. To elucidate the influence of the antibiotic, ampicillin-treated cultures are also comprised within this study and are classified with rates of about 97% and 100% for 532 and 244 nm Raman excitation, respectively. The Raman spectra recorded with 532 nm excitation wavelength show differences of the secondary protein structure and enhanced stress-related respiration rates for the ampicillin-treated cultures. Independent cultural replicates of either ampicillin-challenged or non-challenged cultures are successfully identified with identification rates of over 90%.

Raman Spectroscopy as a Potential Tool for Detection of Brucella spp. in Milk

“…Since in the literature it has been reported that no single classifier is best for all problems and no classifier is always better than another one (39), we decided to perform a comparative study of two known algorithms practicable for bacterial discrimination (46,54).…”

“…Although the resonant excitation in the UV wavelength region probes taxonomic markers, e.g., DNA/RNA vibrations (28,48), the application of visible or NIR Raman excitation wavelengths allows for a phenotypic characterization (20). By applying micro-Raman spectroscopy, even bacterial identification on the single-cell level can be performed (8,15,43,54), and thus elaborate precultivation can be avoided. Thus, the detection process of microorganisms can be accelerated significantly, which is especially important in areas susceptible to bacterial contamination, e.g., clinical environments or the food-processing industry.…”

Phenotypic Profiling of Antibiotic Response Signatures in Escherichia coli Using Raman Spectroscopy

“…Nonetheless, the relatively few articles published to date on the topic point to a significant potential for Raman spectroscopy to become a powerful tool aiding antibiotic drug research. First, it has been shown that Raman spectroscopy can distinguish between bacterial strains resistant and sensitive to a specific antibiotic (22,26). For example, Maquelin et al (22) used Raman spectroscopy with an 830-nm excitation wavelength to analyze Enterococcus faecalis strains sensitive and resistant to vancomycin.…”

Peptide-Guided Surface-Enhanced Raman Scattering Probes for Localized Cell Composition Analysis

“…Peaks at 1,580, 1,383, 1,342, 1,321, 1,139, 1,097, 812, and 660 cm Ϫ1 in the SERS spectra of E. coli (Fig. 3) are commonly assigned to DNA, RNA, or their components (7,9,13,19,21,24). These peaks either (i) shifted, (ii) were significantly reduced in intensity, or (iii) were not present when the pgSERS probes were used.…”

“…The shoulder at 719 cm Ϫ1 in the pgSERS spectrum corresponds to C-C-Nϩ symmetric stretching in phosphatidylcholine, a major constituent of cellular membranes (9). The peak at 744 cm Ϫ1 has been attributed to the membrane-bound cytochromes, hemoproteins that contain heme groups and carry out electron transport (19,23).…”