Identification of Bacillus anthracis via Raman spectroscopy and chemometric approaches

Raman micro-spectroscopy was applied to compile a large-scale database of Raman spectra of single Bacillus endospores and to calculate classification functions, which were trained to discriminate between endospores of 66 strains from 13 Bacillus and Bacillus-related genera including B. anthracis. The developed two-stage classification system comprising two SVM and one LDA classifier was then challenged by a test set of 27 samples to simulate the case of a realworld-scenario, when “unknown samples” are to be identified. In the end, all 27 test set samples including six B. anthracis strains were identified correctly. The samples thereby covered a diverse selection of species within the phylogenetically broad Bacillus genus and also included strains, which were not incorporated in the database before. All of them were correctly identified on species-level with accuracies between 88% - 100%. The sample analysis itself requires no biomass enrichment step prior to the analysis and qualifies the presented Raman spectroscopic approach to be a rapid analysis system in term of Bacillus endospore typing.