Near-infrared Raman spectroscopy has been used for species identification of pure microbial specimens for more than a decade. More recently, this optical method has been extended to the analysis of specimens containing multiple species. In this report, we demonstrate rapid, reagent-free quantitative analysis of a simplified model of oral plaque containing three oral bacteria species, S. mutans, S. sanguis, and S. gordonii, using near-infrared Raman spectroscopy. Raman spectra were acquired from bacterial mixtures in 200 seconds. A prediction model was calibrated by the partial least squares method and validated by additional samples. On a scale from 0 to 1, relative fractions of each species could be predicted with a root mean square error of 0.07. These results suggest that near-infrared Raman spectroscopy is potentially useful in quantification of microbial mixtures in general and oral plaques in particular.
Vol. 2, Iss. 12 Virtual Journal for Biomedical Optics
Qingyuan Zhu, Robert G. Quivey, and Andrew J. Berger, "Raman Spectroscopic Measurement of Relative Concentrations in Mixtures of Oral Bacteria," Appl. Spectrosc. 61, 1233-1237 (2007)