Inhibitory Effects of Mouthwashes on the Cavity-Causing (Cariogenic) Bacterium Streptococcus mutans Figure 1: Analysis of the doubling-time and maximum density of S.mutans grown in various media. Data represent averages of five sample runs. Error bars represent standard deviation. ***p<0.05, ****p<0.01, † p<0.001, †† p<0.05, ††† p<0.01. Figure 2: Analysis of the growth of S. mutans in TS broth with various concentrations of Listerine®. Data represents an average of three sample runs. Abstract: A dental carie (cavity) is defined as damage to the tooth enamel caused by certain bacterial metabolic processes. During the period of time between brushings many layers of bacteria accumulate on the surface of teeth forming what is called a bio-film. One of the early colonizers of this bio- film, Streptococcus mutans, is the bacterium responsible for the carious nature of the bio-film. Anti-cavity mouthwashes are marketed as an effective means of inhibiting the growth of bio-film forming bacteria and thus preventing the formation of caries. The goal of our research is to evaluate the efficiency of various commonly available mouthwashes at inhibiting the growth of S. mutans. We first compared the growth of S. mutans in various media by assessing maximum density and doubling time using plots of optical density versus time. We found that Trypticase Soy Broth (TSB) provided one of the quickest doubling times and the highest maximum density. Using TSB as the growth medium, we found that the growth rate of S. mutans is inhibited by Listerine® in a concentration- dependant manner. Additionally, we plan to compare multiple mouthwashes as well as multiple toothpastes for their effectiveness at inhibiting S. mutans growth using this same methodology. Media Used:  Tripticase Soy Broth (TS)  Brain Heart Infusion Broth (BHI)  Tryptone Yeast Cystine Broth (TYC)  Nutrient Broth (N)  Listerine® Mouthwash Goals/Specific Aims:  Find the most desired media for the growth of S. mutans.  Find a desired concentration of mouthwash that doubles the original doubling time in TS Broth  Find a mouthwash at the desired concentration that inhibits the growth of S.mutans the best. Figure 3: A spectrophotometer. Picture from David B. Fankhauser, Ph.D. University of Cincinnati Clermont College. Figure 4 : Streptococcus mutans. Gram stain. Courtesy of CDC/Dr. R Facklam. Future Studies:  Test various toothpastes using the same methodology.  Colgate Total®  Crest® (original)  Rembrandt®  Sensodyne®  Test various other believed remedies.  Hydrogen Peroxide  Baking Soda  Orange Juice  Salt Water  Determine weather the inhibitory effects are due to bacteristatic growth or if the mouthwashes are bactericidal. Acknowledgements: I would like to thank Dr. Chad Sethman for mentoring this project. I would also like to thank the Waynesburg Universities Center for Research and Economic Development for poster printing and financial support. Conclusions:  S. mutans prefers Trypticase Soy Broth to the other various media  In TSB S.mutans has an average doubling time of minutes  In 5% Listerine ® S. mutans has an average doubling time of minutes  Trends show that the more Listerine® mouth wash that is added the slower the bacteria grows yielding a greater doubling time Ryan Schell*, Tonya Tanner*, and Dr. Chad R. Sethman Waynesburg University Department of Biology