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ListerLab2 - Special Research Projects Bacteria...

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Special Research Projects: Bacteria: Inactivation by Chemical and Physical Agents: New vs. “Old” Listerine BioS 42-062 April 30 th , 2007
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Introduction: Listerine was created in 1879 by Dr. Joseph Lawrence and Jordan Lambert originally as an antiseptic for surgical disinfection, and is named Listerine after Sir John Lister who in 1865 performed the first antiseptic surgery. Over time the solution was found useful for many uses, and in 1895 it was first marketed as an oral antiseptic and rinse, a purpose for which it is commonly used today. Listerine is advertised as intended to fight “bad breath germs that can cause the gum disease gingivitis.” According to the Listerine manufacturer’s website, “The power of LISTERINE® Antiseptic comes from a formula of 4 essential oils that kill millions of germs on contact. Our fixed combination of eucalyptol, menthol, methyl salicylate, and thymol continues to deliver unsurpassed results. No other branded mouthwash has this formula; that’s why no other mouthwash is like Listerine Antiseptic.” According to the drug facts listed on the product, Listerine contains the following active ingredients in concentration (%) by volume: Eucalyptol . 092%, Menthol .042%, Methyl salicylate .060%, Thymol .064%. The “Cool Mint” Listerine that we used also contained 21.6% alcohol by volume, and this was listed as an “inactive ingredient.” According to the Listerine website’s FAQ’s section, “Why is alcohol needed in Listerine Antiseptic Mouthwash? Alcohol is used as a solubilizer for flavors and active ingredients (the fixed combination of four essential oils: eucalyptol, menthol, methyl salicylate and thymol).” Alcohol is included in the solution of Listerine to make the hydrophobic (and often solid at room temperature) active essential oils soluble, and is not listed as actively killing bacteria in the mouth. Escherichia Coli bacteria are extremely prevalent in the lower intestines of mammals including human beings. The bacteria itself was discovered in 1885 by
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Theodor Escherich, and contains hundreds of different strains, many of which are responsible for illnesses in humans exposed to bacteria outside of their digestive tract, and can cause severe cramps and diarrhea. E coli bacteria grow best in vivo (~37 °C) or at slightly higher temperatures. E coli is used often in biological studies because it is so common and well studied. Because E coli is extremely contagious and contaminates easily, a proper and thorough sterile technique is necessary. For the sake of this experiment, we will be comparing the effectiveness of “Cool Mint” Listerine with a listed expiration date of May 1998, to a sample of the same brand and flavor that is within the 2 year shelf life prescribed by the manufacturer, in killing or inactivating E coli bacteria when adhering most closely to the manufacturer’s guidelines.
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