In-Vitro Studie Englisch


3) Project results

A) Determination of the minimum inhibitory concentration (MIC) of BlueM

    S. mutans cells were cultivated overnight in BHI broth. Cells were diluted to the same
    density at 600 nm and used immediately to determine the MIC. BHI broth was used as
    medium and different concentrations (0; 0.01; 0.1; 1; 2; 4; 10% (vol/vol)) of BlueM
    mouthwash were tested in sterile 96-well microtiter plates. Chlorhexidine (0; 0.01; 1;
    2; 4; 10 μg/ml (wt/vol)) was used as control. Plates were incubated overnight at 37°C
    in air with 5% CO2. A microplate reader was used to determine the absorbance at
    600 nm. The MIC was determined as the lowest concentration of BlueM mouthwash
    or chlorhexidine that inhibited the visible growth of S. mutans cells. All experiments
    were performed using three independent cultures of S. mutans. Our results showed
    that under our tested conditions, the MIC of BlueM mouthwash was 1%, while the
    MIC of chlorhexidine (control) was 10 μg/ml for S. mutans caries pathogens.

B) Antibiofilm activity of BlueM mouthwash

    We assessed the in vitro susceptibility of S. mutans caries pathogens to BlueM
    mouthwash. In order to mimic the short exposure to a mouth rinse, biofilms of
    S. mutans (6-h-, 1-day-, and 3-day-old) were exposed for 60 sec. In order to kill
    biofilm cells, a concentration of 10 ´MIC is recommended. For the experiments
    involving biofilm cells, we then tested a concentration of 10% (vol/vol) and
    100 μg/ml (wt/vol) of BlueM mouthwash and chlorhexidine, respectively. Exposure
    of biofilms to sterile saline was used as negative control. The results are presented at
    Figure 1 below.

Figure 1. Antibiofilm activity of BlueM mouthwash against S. mutans caries
pathogens. CHX: chlorhexidine; BlueM: BlueM mouthwash. Treatment (60 sec) with
sterile saline was used to determine the viable biofilm cell number. The percentage of
cell survival was determined by comparing the cell counts of treated-biofilms with
that of saline controls. *, P value <0.05.

Our results showed that at a concentration of 10% (vol/vol), BlueM mouthwash was
effective at reducing the viability of S. mutans biofilms by 98% (6-h-old biofilm),
99.9% (1-day-old biofilm), and 99.9% (3-day-old biofilm). In contrast, chlorhexidine
treatment of 60 s at 10 ´MIC failed to reduce biofilm cell viability (Table 1).

In conclusion, BlueM mouthwash solution is effective in killing unicellular
(plantonkic) and multicellular (biofilm) of S. mutans caries pathogens, and more
effective than chlorhexidine. Interestingly, BlueM is particularly effective at killing
older thicker biofilms (3-d-old) that are usually less susceptible to antimicrobial
treatments than younger biofilms.

                 Date: January 24, 2018

Dr. Céline M. Lévesque
Associate Professor, Oral Microbiology, Faculty of Dentistry, University of Toronto
Canada Research Chair in Oral Microbial Genetics
Honorary Associate Professor, Faculty of Dentistry, The University of Hong Kong

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