Lecture 18 Outline
Antibacterial soaps, Listerine, and Lysol
Alcohols are the most common antiseptics
alcohols can kill bacteria and fungi, but are not effective against endospores or nonenveloped viruses
alcohols act by denaturing (unfolding) proteins and disrupting cell membranes by solubilizing fats
some water is needed for protein denaturation and usually 70% alcohol with water is used
alcohols are not good for wounds since they coagulate the surface tissue but the bacteria can grow beneath this layer
the two top alcohols are ethanol and isopropanol (rubbing alcohol)
tinctures are alcohol solutions in combination with another antiseptic
for example, tincture of iodine is 1% iodine in 70% aqueous ethanol
it is used as a surgical scrub
heavy metals are also toxic to microbes and used as antiseptics
mercury has the longest history of any antiseptic, it has a broad spectrum and is bacteriostatic
silver also has a long history and is still used for infections in the mouth and eye
copper is generally used as an algicide to kill algae
zinc chloride is a common ingredient in mouthwash
Phenolics
Lister first suggested the used of phenol (carbolic acid) for sterilization in surgery
the problem with phenol is that it is very irritating and has a bad odor
today phenol is still used in throat lozenges and in throat sprays
phenolics are organic compounds similar to phenol but without the bad smell and irritancy of phenol
the active ingredient in Lysol is ortho-phenylphenol
it is derived from coal tar and is a class of compounds called cresols
Lysol is also 79% alcohol, enhancing the effectiveness of the phenylphenol
another cresol is hexachlorophene, used as a surgical scrub and the active ingredient in pHisoHex
hexachlorophene is also used in toothpaste, deodorants and soaps
it is effective against Staphylococci and Streptococci common skin pathogens
phenolics are good disinfectants because they are stable and persistent
Listerine is another common antiseptic and was first concocted by Lister in 1879
Warner-Lambert picked it up in 1881 and today it is a $400 million per year product
Listerine is a mixture of thymol, eucalyptol, menthol and methyl salicylate: natural products ("essential oils") that include phenolics
Listerine also contains over 25% alcohol which enhances its effectiveness
phenolics act by disrupting cell membranes, inactivating enzymes, and denaturing proteins
Soap, detergents and surfactants
soaps act merely to suspend particles during scrubbing
soaps are not disinfectant, but help remove bacteria from surfaces
often an antiseptic compound, like triclosan, is added to the soap
surfactants are surface active agents that act to decrease surface tension
the most common surfactant disinfectants include quaternary ammonium compounds (Quats)
Quats have a long fatty tail (like a lipid) with a positively charged N at one end
variations of benzalkonium chloride are commonly added to laundry detergents and household cleaners like Formula 409
another popular Quat is cetylpyridinium chloride commonly called Cepacol
if your mouthwash bubbles when you shake it then it contains a Quat
Quat are colorless, odorless, tasteless, stable, and non-toxic, but they are also short-lived and easily inactivated
Quats are effective against bacteria, fungi and enveloped viruses, but not active against endospores and nonenveloped viruses
Quats act by disrupting the cell membrane and proteins
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