Development of Dental Plaque Microplate Biofilm Microcosms

We have previously examined antimicrobial effects of chlorhexidine and essential oils on biofilm growth of Streptococcus mutans and Lactobacillus plantarum. Objectives: To develop a procedure to study dental plaque microcosm biofilms evolved from the natural mixed oral microbiota in microplates that would be suitable for the screening of potential antimicrobial agents. Methods: Triplicate plaque biofilms were cultured with daily renewal of media on “Thermanox” coverslips in 24-well microplates from plaque-enriched human saliva of two donors. The effect of different simulated oral fluids (artificial saliva DMM, complex media BMM, BM) and sucrose concentrations, on pH and planktonic growth were measured daily. The final plaque biofilm biomass was analysed for 40 microbial species by checkerboard DNA:DNA hybridisation (CKB) analysis. Results: CKB analysis showed a gradual increase in the level of anaerobes and a decrease in streptococci and the microbiota composition differed in DMM compared with BMM and BM which were similar. The amount of biofilm growth was different with the two donors. In the absence of sucrose, the daily pH change was an increase of 1 pH unit, in 0.15% sucrose it was unchanged, and in 0.50% sucrose decreased to pH 4.0 reducing microbial growth. Conclusions: The ‘Microplate Biofilm Microcosms’ can provide a basis for more detailed studies in the ‘Multiplaque Artificial Mouth and help explain findings in complex plaque biofilm systems. This system also has potential for screening anti-plaque agents such as essential oils against dental biofilms. We thank Lisa Gellen for the checkerboard analysis. This work was supported by, the Health Research Council of New Zealand, the New Zealand Lottery Board and a Wellington Medical Research Foundation summer studentship (to K.S).