Blue light suppresses black pigmented bacteria

[sadman]

2967 Blue light suppresses black-pigmented bacteria in microcosm biofilms
K. RUGGIERO1, A. ABERNETHY1, A.G. DOUKAS2, J.M. GOODSON1, and N.S. SOUKOS1, 1Forsyth Institute, Boston, MA, USA, 2Massachusetts General Hospital, Boston, USA

Objectives: To test the susceptibility of oral black-pigmented bacteria to blue light in planktonic phase and dental plaque microcosm laboratory biofilms. Methods: Suspensions of Porphyromonas gingivalis and Prevotella intermedia were exposed to blue light of 455 nm with a power densitiy of 100 mW/cm2 for 15, 30 and 60 seconds. Multi-species oral biofilms developed on blood agar in 96-well plates from dental plaque inocula were also exposed to blue light with a power densitiy of 50 mW/cm2 for 20 seconds. Four consecutive illuminations were given to these biofilms (one exposure every day). The susceptibility of microorganisms to light in planktonic and biofilm phase was evaluated by a colony forming assay and DNA probe analysis respectively. Results: Light produced 50% and 90% killing of P. gingivalis and P. intermedia in vitro respectively. In biofilms, no reduction in the proportion of black-pigmented species (P. gingivalis, P. intermedia, Prevotella nigrescens and Prevotella melaninogenica) was found after two light exposures. At day 3, there was a slight reduction of black-pigmented species compared with controls. By day 4, however, the proportion of black-pigmented bacteria was reduced by 40%. Conclusions: These data show that successive illuminations may lead to a cumulative suppressive effect on dental plaque black-pigmented microorganisms. In a clinical setting, this could lead to a gradual shift of the microbial composition towards a new one associated with health. Supported by NIDCR (RO1-DE-143