Following the Mechanisms of Bacteriostatic versus Bactericidal Action Using Raman Spectroscopy

Abstract

Antibiotics cure infections by influencing bacterial growth or viability. Antibiotics can be divided to two groups on the basis of their effect on microbial cells through two main mechanisms, which are either bactericidal or bacteriostatic. Bactericidal antibiotics kill the bacteria and bacteriostatic antibiotics suppress the growth of bacteria (keep them in the stationary phase of growth). One of many factors to predict a favorable clinical outcome of the potential action of antimicrobial chemicals may be provided using in vitro bactericidal/bacteriostatic data (e.g., minimum inhibitory concentrations-MICs). Consequently, MICs are used in clinical situations mainly to confirm resistance, and to determine the in vitro activities of new antimicrobials. We report on the combination of data obtained from MICs with information on microorganisms' "fingerprint" (e.g., DNA/RNA, and proteins) provided by Raman spectroscopy. Thus, we could follow mechanisms of the bacteriostatic versus bactericidal action simply by detecting the Raman bands corresponding to DNA. The Raman spectra of Staphylococcus epidermidis treated with clindamycin (a bacteriostatic agent) indeed show little effect on DNA which is in contrast OPEN ACESSMolecules 2013, 18 13189 with the action of ciprofloxacin (a bactericidal agent), where the Raman spectra show a decrease in strength of the signal assigned to DNA, suggesting DNA fragmentation.

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

“…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. The Raman spectra of S. epidermidis treated with bacteriostatic clindamycin revealed little effect on DNA, which is in contrast with the action of the bactericidal agent ciprofloxacin, where the Raman spectra showed a decrease in strength of the signal assigned to DNA, suggesting DNA fragmentation and cell death …”

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“…The plate showing 99.9 per cent inhibition, in comparison to the initial count of the original inoculums, was considered to be as MBC. For all the assays 0.5 McFarland opacity culture was used 13,14,15 . All the assays were carried out in triplicate.…”

Quantitative Raman Spectroscopy Analysis of Polyhydroxyalkanoates Produced by Cupriavidus necator H16

“…Raman spectroscopy has an extremely competitive position if in situ, contactless, noninvasive, and fast analysis is required, say, on-line in biotechnological processes. The sample does not have to be prepared for analysis using solvents; the technique is label free with minimal interference from water [8,9,10,11,12,13,14,15,16,17,18,19]. …”