Implemented through a confocal microscope, Raman spectroscopy has been used to distinguish between biofilm
samples of two common oral bacteria species, Streptococcus sanguinis and mutans, which are associated with
healthy and cariogenic plaque, respectively. Biofilms of these species are studied as a model of dental plaque. A
prediction model has been calibrated and validated using pure biofilms. This model has been used to identify
the species of transferred and dehydrated samples (much like a plaque scraping) as well as hydrated biofilms in
situ. Preliminary results of confocal Raman mapping of species in an intact two-species biofilm will be shown.
Confocal Raman microspectroscopy is used to discriminate between different species of bacteria grown in biofilms. Tests are performed using two bacterial species, Streptococcus sanguinis and Streptococcus mutans, which are major components of oral plaque and of particular interest due to their association with healthy and cariogenic plaque, respectively. Dehydrated biofilms of these species are studied as a simplified model of dental plaque. A prediction model based on principal component analysis and logistic regression is calibrated using pure biofilms of each species and validated on pure biofilms grown months later, achieving 96% accuracy in prospective classification. When biofilms of the two species are partially mixed together, Raman-based identifications are achieved within ~2 µm of the boundaries between species with 97% accuracy. This combination of spatial resolution and predication accuracy should be suitable for forming images of species distributions within intact two-species biofilms.