Bacterial identification in real samples by means of micro-Raman spectroscopy

Abstract

Pathogen detection is essential without time delay especially for severe diseases like sepsis. Here, the survival rate is dependent on a prompt antibiosis. For sepsis three hours after the onset of shock the survival rate of the patient drops below 60 %. Unfortunately, the results from standard diagnosis methods like PCR or microbiology can normally be received after 12 or 36 h, respectively. Therefore diagnosis methods which require less cultivation or even no cultivation at all have to be established for medical diagnosis. Here, Raman spectroscopy, as a vibrational spectroscopic method, is a very sensitive and selective approach and monitors the biochemical composition of the investigated sample. Applying micro-Raman spectroscopy allows for a spatial resolution below 1 µm and is therefore in the size range of bacteria. Raman spectra of bacteria depend on the physiological status. Therefore, the databases require the inclusion of the necessary environmental parameters such as temperature, pH, nutrition, etc. Such large databases therefore require a specialized chemometric approach, since the variation between different strains is small. In this contribution we will demonstrate the capability of Raman spectroscopy to identify pathogens without cultivation even from real environmental or medical samples.

Fast and robust identification of single bacteria in environmental matrices by Raman spectroscopy

“…Studies conducted on bacteria cultivated under various conditions (medium, temperature, age) indicate that identification at the species or even strain level is possible, provided a comprehensive database containing spectra from all relevant conditions is employed 4 , 5 . Similar findings were reported for bacteria measured directly in patients' cerebrospinal fluid 6 , 7 , and tap water 8 .…”

Raman spectroscopy: techniques and applications in the life sciences

“…a model classifying spectra into more than two groups). This has been used by several groups to identify stages of the cell cycle [135], species of bacteria [485], skin cancer [147], and tumor metastasis to other tissues [486].…”