Download Mouthwash Effectiveness Against Oral Bacteria

Mouthwash Effectiveness Against Oral Bacteria
David Allen Adams
Biology Undergraduate
Department of Biology
Tennessee Tech University
Cookeville, TN 38505
Abstract:
Bacteria can cause many complications in the mouth. Rinsing with mouthwash may
prevent some of these problems. The objective of this research is to determine the susceptibility
of bacteria to different mouthwashes. Three types of oral bacteria will be grown on agar plates.
The plates will be divided into four quadrants. Discs soaked in the mouthwashes will be placed
in separate quadrants. One quadrant will contain a disc containing water as a control. The
susceptibility of each mouthwash will be evaluated based on the zone of inhibition around the
disc. The hypothesis is little variation will occur between the different mouthwash brands.
Key Words:
Bacteria, mouthwash, anti-microbial susceptibility, antiseptic, Pseudomonas, Escherichia,
Staphylococcus, oral complications, bacterial inhibition
Introduction:
Oral bacteria can cause several health complications. Halitosis is one problem caused by
bacteria in the mouth. “Undesirable oral odors generally come from sulfur-containing proteins
and peptides hydrolyzed by gram-negative bacteria, and alkaline environment” (McDowell and
Kassebaum 1993). Tooth decay is another negative result of oral bacteria. “Sugars and other
fermentable carbohydrates, after being hydrolyzed by salivary amylase, provide substrate for the
actions of oral bacteria, which in turn lower plaque and salivary pH. The resultant action is the
beginning of tooth demineralization” (Touger-Decker and Loveren 2003). Other oral problems
can be associated with bacteria. “Bacteria in the mouth are primarily responsible for gingivitis
and periodontal disease” (Journal of American Dental Association 1998).
One can practice several procedures to reduce the negative effects of oral bacteria.
Brushing, flossing, and rinsing with mouthwash on a regular basis can drastically reduce
problems associated with bacteria. Antimicrobial agents such as mouthwash are especially useful
in lowering the number of oral bacteria. “The number of viable (capable of living) bacteria
dropped by 94% after rinsing with antiseptic mouth rinse” (Fine et. al 1993).
This study was performed to test the effectiveness of different brands of mouthwash on
the growth of oral bacteria. The effectiveness can be determined by measuring the zone of
inhibition formed by each mouthwash. The bacteria will either be susceptible, resistant, or
intermediate to each mouthwash. The objective of this research is to determine the susceptibility
of Staphylococcus, Escherichia, and Pseudomonas to three different brands of mouthwash. The
Null Hypothesis is no difference in bacterial growth will exist between rinsing with water and
rinsing with mouthwash.
Methods and Materials:
Methods were derived from the 2004 Medical Microbiology 4750/5750 Lab Manual by
Dr. Goss. The experiment took place in the microbiology lab (Room 402) in Pennebaker Hall.
Three different TSA plates were inoculated with Staphylococcus, Escherichia, and Pseudomonas.
The plates were incubated for 24 hours. Each plate was divided into four separate quadrants (See
Figure 1). Three of the quadrants contained paper discs soaked in three different brands of
mouthwash: Scope (B), Listerine (C), and Equate (D). The remaining quadrant contained a paper
disc soaked in water as a control (A). A total of three trials were performed. Averages of the
inhibition zone sizes, in millimeters, were taken.
Staphylococcus
Escherichia
Pseudomonas
A
B
A
B
A
B
D
C
D
C
D
C
Figure 1. Disc Diffusion
Results:
Each genus of bacteria was susceptible to all three brands of mouthwash. Water had no
affect on bacterial growth. Figure 2 gives a graphical interpretation of the results.
18
18
16
16
Inhibition Zone (mm)
14
12
12
10
8
8
9
8
8
7
8
6
4
0
0
2
Staphylococcus
0
0
Pseudomonas
Water
Mouthwash A
Escherichia
Mouthwash B
Mouthwash C
Escherichia
Pseudomonas
Staphylococcus
Figure 2. Mouthwash Comparison
Discussion:
Bacteria are the cause of many oral complications. Some of these problems are minor
such as undesirable oral odors (McDowell and Kassebaum 1993). Tooth demineralization is a
more serious problem (Touger-Decker and Loveren 2003). Gingivitis and periodontal disease
are other major problems caused by bacteria (Journal of American Dental Association 1998).
Using antiseptic mouth rinse along with brushing and flossing can help alleviate these problems.
The bacteria proved to be susceptible to all three brands of mouthwash. Inhibition of
bacterial growth due to disc diffusion showed proof of mouthwash effectiveness. However, there
was a variation in susceptibility among the bacteria. Staphylococcus was the most susceptible
with the greatest average zone of inhibition. Escherichia and Pseudomonas were equally
susceptible to the mouthwashes.
Better results may be obtained by testing a greater total number of different oral bacteria.
This experiment was limited to only three types of bacteria due to plate availability. Testing a
greater variety of oral pathogenic bacteria would provide more accurate results. The organisms
used in this experiment were mainly normal flora organisms. One study showed “the number of
viable bacteria dropped by 94% after rinsing with antiseptic mouth rinse” (Fine et. Al 1993).
Results such as these could not be produced by this experiment. No colony counts were taken,
nor were treated plates compared to untreated ones.
Conclusions:


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
Water had no affect on bacterial growth
All three mouthwash brands inhibited bacterial growth
Staphylococcus was most susceptible
Pseudomonas and Escherichia were equally susceptible
The generic brand mouthwash, Equate, was most effective
More cost does not always equal better value
Acknowledgements:
I would like to thank Dr. Goss for assisting in my research. Her help was much
appreciated. I would also like to thank Tennessee Tech for allowing me to use their facility and
equipment.
Literature Cited:
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Fine, Daniel , Julie Yip, David Furgang, Michael Barnett, Arnold Olshan, and Jack
Vincent. 1993. Reducing bacteria in dental aerosols: pre procedural use of an antiseptic
mouthrinse. Journal of the American Dental Association 124:56(3).
Goss, Susan. 2004. Disc Diffusion Assay. Medical Microbiology Laboratory Manual
4750/5750: 4-6
McDowell, John ,and Denise Kassebaum. 1993. Diagnosing and treating halitosis.
Journal of the American Dental Association 124:55(10)
Touger-Decker, Riva ,and Cor van Loveren. 2003. Sugars and dental caries. American
Journal of Clinical Nutrition 78:881(12)
Periodontal diseases: pathogenesis and microbial factors. Journal of the American Dental
Association 1998. 129:58(5)
Appendix:
Staphylococcus
Water
Inhibition Zone
mm
Trial 1
Trial 2
Trial 3
Average
0
0
0
0
Mouthwash A
17
14
16
16
Mouthwash B
Mouthwash C
14
10
13
12
18
18
17
18
Mouthwash B
Mouthwash C
8
7
7
8
9
8
8
8
Mouthwash B
Mouthwash C
7
8
7
7
8
9
9
9
Escherichia
Water
Inhibition Zone
mm
Trial 1
Trial 2
Trial 3
Average
0
0
0
0
Mouthwash A
8
8
8
8
Pseudomonas
Water
Inhibition Zone
mm
Trial 1
Trial 2
Trial 3
Average
0
0
0
0
Mouthwash A
8
7
8
8