Blog Assignment #6: Research Introduction- The Effects of Mouthwash on Bacteria

Group Project Blog Post: The Effects of Mouthwash on Bacteria

Team Members: Hazel Hosseini, Greyson Hamilton, Michelle Le, Eloina Rodriguez

Description: Our group decided to look at the effects of mouthwash on oral bacterial growth. We noticed that some mouthwashes are labelled as antibacterial while others are labelled as antiseptic. After comparing the ingredients in different kinds of mouthwashes, we identified a common active ingredient Cetylpyridinium chloride in antibacterial mouthwashes which led us to predict that it would significantly inhibit the growth of bacteria in comparison to mouthwashes that did not contain Cetylpyridinium chloride. We took in consideration the possibility that the effectiveness of a mouthwash may differ in different people and decided to use bacterial samples from three different people.

Hypothesis:Antibacterial mouthwashes containing Cetylpyridinium chloride will be more effective against bacterial growth than mouthwashes that do not contain it.

Predictions: The petri dishes with Cetylpyridinium chloride will have less bacterial growth than others without Cetylpyridinium chloride. The control with DI water will have the most bacterial growth, as it will not be inhibited by chemicals.

Updates: As of May 11th we have run our first trial. We found more growth in plates treated with listerine than the plates treated with crest with scope and crest clinical. We saw comparable inhibition of growth in the CPC (Cetylpyridinium chloride) treated plates as we did in crest clinical, which contains 0.1% CPC. We saw some unexpected growth in one of our plates where it grew under the crest clinical treated cotton disk, we want to repeat this next week to see if some of the bacteria on this plate are resistant to crest clinical or if it was simply an error on our part.

Challenges: When analyzing our first trial results we had an unusual result in one of our LIsterine Naturals samples. It seemed that bacteria had grown back over a distinct zone of inhibition around the paper disk which could be due to an error. It also appeared that our bacterial sample on the plates was not even on all the plates. On one plate in particular, it made it difficult to distinguish the actual area of inhibition.

Decision to do Project: We chose to do this project because we wanted to test the effects of chemicals on organisms. Bacteria are perfect test subjects as they can be readily grown and grown at a quick rate. We wanted to test the effectiveness of mouthwashes in regard to the inhibition of bacterial growth, because it has real world applications. In our first trial the results suggest not all mouthwashes are as effective in the inhibition of bacterial growth, and they vary largely in end result. We might expand this project later to encompass other useful applications in regard to understanding our oral bacteria.

Sources: In order to measure and compare the effectiveness of mouthwash on bacterial growth we researched methods of measuring microbial growth.  "Kirby-Bauer Disk Susceptibility Test" on Boundless Microbiology explains the Kirby-Bauer method of measuring the sensitivity of bacteria to an antibiotic by placing a paper disk of an antibiotic on an agar with a pure culture of bacteria. It also describes that after incubation, a clear area around the paper disk called the “zone of inhibition” indicates the sensitivity of a bacteria to that particular antibiotic. The diameter of the “zone of inhibition” can be measured in millimeters to identify the sensitivity of the bacteria to that antibiotic.

Boundless. "Kirby-Bauer Disk Susceptibility Test." Boundless Microbiology Boundless. 13 Aug. 2016. [cited 23 Apr. 2017] https://www.boundless.com/microbiology/textbooks/boundless-microbiology-textbook/antimicrobial-drugs-13/measuring-drug-susceptibility-157/kirby-bauer-disk-susceptibility-test-791-6152/