Identification of bacteria in a bacterial mixture using Raman spectroscopy

The need for a quick, accurate and reliable method for detection of pathogenic bacteria, especially in mixture, is increasing day by day. A lot of detection methods have been developed since the discovery of the first microorganism, most of which are based on biochemical and immunological properties. However, their long sample preparation and procedure times, expensive and heavy instrumentation and need for both well- educated and trained staff are some of the disadvantages of these methods.Raman spectroscopy is a promising technique for fast detection and identification of bacterial cells. It can be applied directly on the sample and there is no need for pre- test procedures.Considering the facts about Raman spectrometry which is a fast, reliable and feasible method for identification of bacterial cells in a mixture was the goal of this study. To achieve this goal five different bacteria (BFK13, BHK7 and DH5alpha varieties of Escherichia coli, Proteus vulgaris and Shigella sonnei) were used together as a model. First, the binary and ternary mixtures of bacteria were prepared. Then, Raman spectra were obtained from particular microorganism and their binary and ternary mixtures. When collected data were processed and statistically analyzed using SPSS software they were applied to plot 2D charts of Euclidean distance. As a result, it was shown that Raman spectra of each bacterium and their mixtures are very similar. However, each spot representing spectra of species fall at different coordinate on 2D charts of Euclidean distance.