Mouthwash Effectiveness in Eliminating Bacteria

1
Mouthwash Effectiveness in Eliminating Bacteria

• By Matthew Mancuso
• Department of Biology
• Tennessee Technological University, Cookeville,
  TN 38505

2
Overview

• Introduction
• Background
• Hypothesis
• Materials, Methods, and Data Collection
• Timelines
• Expected Results
• Benefits

3
Introduction

• This will test the effectiveness of several kinds
  of mouthwash which claim to be antibacterial
  Scope, Listerine, and Cepasol.
• Against several common strains of bacteria found
  in the mouth Genus Streptococcus, Bacillus, and
  Pseudomonas.

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Objective

• To determine if commercially available
  mouthwashes are capable of performing the
  advertised elimination of common oral bacteria.

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Experimental

• Tests will be run both with dilutions of the
  mouthwash samples in tubes, and streak plates
  with discs treated with mouthwash.
• These will determine the strength of the
  antimicrobial agent in the mouthwash, as well as
  its ability to inhibit formation of new bacterial
  colonies.

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Expectations

• All 3 brands contain alcohol, which is effective
  in killing bacteria in solution, the tubes should
  show a correlation between alcohol and ability
  to eliminate bacteria.
• On the plates the alcohol will evaporate leaving
  only the antibacterial agents to slow the growth
  of bacteria, these will show the strength of the
  other antimicrobial agents in the mouthwash.

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Background

• Data recorded in these tests should correlate
  with other studies on similar effects of
  mouthwashes.
• These include dilution tests which suggest the
  effectiveness of alcohol, as well as active
  ingredient tests.

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Journal Sources

• The Effect of Mouthwash on the Bacteria Found in
  the Mouth Over a Period of Time. Dana A.
  Blackburn (Bulletin of the South Carolina Academy
  of Science, Annual 2003)
• The Role of Therapeutic Antimicrobial
  Mouthrinses in Clinical Practice. Michael L.
  Barnett. (Journal of the American Dental Assoc,
  June 2003 )
• Effects of a Chlorhexidine Gluconate
  Containing Mouthwash on the Vitality and
  Antimicrobial Susceptibility of In Vitro Oral
  Bacterial Ecosystems. Robert G. Bartolo Andrew
  J. McBain Carl E. Catrenich Duante Charbonneau
  Ruth G. Ledder Peter Gilbert. (Applied
  Environmental Microbiology Aug. 2003)
• The Antimicrobial Effect of Mouth Rinses When
  Used for 15 Seconds. Darcie Bell Laura Bretsch
  Michael Lents James D Kettering. (Journal of
  Dental Hygiene, Fall 2000)

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Hypothesis

• Antimicrobial mouthwashes are effective at
  killing bacteria but not as effective as the
  product labeling suggests.

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Materials Plates

• Bacteria Millions of each, Streptococcus,
  Pseudomonas, and Bacillus, bacteria commonly
  found on food and in the mouth.
• Agar plates 12, one for each type of
  bacteria/mouthwash pairing and 3 for control.
• Testing discs (60)5 per plate, this will give
  many sets of data for each mouthwash while not
  wasting plates.

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Methods Plates

• Each of the 3 species of bacteria will be
  cultured in broth then applied in streaks to agar
  plates so the bacteria are evenly distributed
  about the surface.

12
Methods Plates

• Discs soaked in each of the different mouthwashes
  will then be applied to the agar plates (1 type
  per plate), and discs soaked in water will be
  applied to the control.

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Methods Plates

• After the bacteria is allowed to incubate for
  several days the zones of inhibition (area around
  the discs where no bacteria is growing) will be
  measured.

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Methods Plates

• The size of the zone corresponds to the ability
  of the antimicrobial agent in the mouthwash to
  inhibit the growth of bacteria.

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Data Collection Plates
Bacillus Agar Plate Results Agar Plate Results Agar Plate Results Agar Plate Results
Inhibition radius in mm from disc Inhibition radius in mm from disc Inhibition radius in mm from disc Inhibition radius in mm from disc
Disc
1 2 3 4 5
Scope
Listerine
Cepasol
Control
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Materials Tubes

• Test tubes60, for each of the 3 mouthwash to be
  mixed at each of 5 dilutions (1, 11, 110,
  1100, 11000) and each to be paired with the 3
  different bacteria, and 15 for the control, a
  dilution of common laboratory antiseptic to which
  the results may be compared .
• Broth nutrient broth to be used in each of the
  test tubes as the diluting agent.
• No other lab equipment will be necessary, as
  results will be immediately visible to the naked
  eye.

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Methods Tubes

• The first test tube of each dilution is first
  filled with 110mL of the pure mouthwash.
• The 4 subsequent tubes are filled with 90mL of
  broth.

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Methods Tubes

• 10mL of liquid is then removed from the 1st tube
  and placed into the 2nd, making this mixture 1/10
  as strong as the original, this is continued from
  the 2nd to the 3rd, 3rd to the 4th, and 4th to
  the 5th.

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Methods Tubes

• After a few days each tube will be examined to
  determine if bacteria are growing in it,
  typically indicated by sediment and cloudiness of
  the broth.
• Then the lowest concentration of mouthwash with
  no bacteria growing in it can be compared to the
  control to determine the strength of the
  antimicrobial agents in each type.

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Data Collection Tubes
Bacillus Test Tube Results Test Tube Results Test Tube Results Test Tube Results
Bacteria present (pos. or neg.) Bacteria present (pos. or neg.) Bacteria present (pos. or neg.) Bacteria present (pos. or neg.)
Dilution
1 1/10 1/100 1/1,000 1/10,000
Scope
Listerine
Cepasol
Control
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Timelines

• Preparation of each set of tests should take less
  than 1 day.
• Incubation should be run for 2 or 3 days to be
  sure maximum growth has occurred.
• Examination of the results should take less than
  1 day as well.

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Expected Results

• It is expected to see a correlation between
  alcohol and bacteria killed in solution as
  alcohol is a known antimicrobial.
• Results from the various antiseptics in the
  products should vary as the effectiveness of
  these specific chemicals on the bacteria may be
  different, though it is expected that Listerine,
  having more antimicrobial substances should prove
  more effective than the other 2.

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Benefits

• This research should help a person to decide what
  mouthwash to purchase based upon its contents and
  not just the claims listed on the bottle.