Identification of vancomycin interaction with Enterococcus faecalis within 30 min of interaction time using Raman spectroscopy

Abstract

Vancomycin is an important glycopeptide antibiotic which is used to treat serious infections caused by Gram-positive bacteria. However, during the last years, a tremendous rise in vancomycin resistances, especially among Enterococci, was reported, making fast diagnostic methods inevitable. In this contribution, we apply Raman spectroscopy to systematically characterize vancomycin-enterococci interactions over a time span of 90 min using a sensitive Enterococcus faecalis strain and two different vancomycin concentrations above the minimal inhibitory concentration (MIC). Successful action of the drug on the pathogen could be observed already after 30 min of interaction time. Characteristic spectral changes are visualized with the help of multivariate statistical analysis (linear discriminant analysis and partial least squares regressions). Those changes were employed to train a statistical model to predict vancomycin treatment based on the Raman spectra. The robustness of the model was tested using data recorded by an independent operator. Classification accuracies of >90 % were obtained for vancomycin concentrations in the lower range of a typical trough serum concentration recommended for most patients during appropriate vancomycin therapy. Characterization of drug-pathogen interactions by means of label-free spectroscopic methods, such as Raman spectroscopy, can provide the knowledge base for innovative and fast susceptibility tests which could speed up microbiological analysis as well as finding applications in novel antibiotic screenings assays. Graphical Abstract E. faecalis is incubated with vancomycin and characterized by means of Raman spectroscopy after different time points. Characteristic spectral changes reveal efficient vancomycin-enterococci-interaction.

The application of Raman spectroscopy for the detection and identification of microorganisms

“…To deeper understand the Raman signals upon vancomycin–enterococci interaction, another study followed this interaction over a time span of 90 min using a sensitive E. faecalis strain and two different vancomycin concentrations above the minimal inhibitory concentration. After 30 min, a successful action of the drug on the pathogen could already be observed, and the spectral changes were explained using biological knowledge of the mode of action of the antibiotics …”

“…The demonstration that the spectral differences in the Raman spectra of treated and untreated pathogens are not a result of the pure presence of the antibiotic was shown by comparing the spectra without treatment and immediately after antibiotic treatment. No significant differences could be identified …”

“…No significant differences could be identified. [89,122,155] An inexpensive, portable Raman system was used to investigate the effect of fluoroquinolone ciprofloxacin treatment on the three common UTI-causing bacteria E. coli, K. pneumoniae, and Proteus strains. It was possible to distinguish treated and sensitive bacteria from bacteria that were not treated with the antibiotic.…”

“…After 30 min, a successful action of the drug on the pathogen could already be observed, and the spectral changes were explained using biological knowledge of the mode of action of the antibiotics. [155] Further, antibiotic influence was addressed in the focus of the effect of the antibiotic agent, which can be bacteriostatic or bactericidal. Bernatova et al reported a procedure to follow mechanisms at the single-cell level of the bacteriostatic versus bactericidal action simply by detecting the Raman bands corresponding to DNA.…”

Bacteria Hunt Bacteria through an Intriguing Cyclic Peptide

“…Vancomycin‐resistant MRSA carries transposon Tn1546, and this resistance occurs through horizontal transfer of the mobile genetic elements encoding the resistant genes from vancomycin‐resistant E. faecalis . Resistance to vancomycin was first described among Enterococcus and Enterococci (VRE), in which various types of resistance operons were found located on the plasmid and/or chromosome …”