A student is shopping for antibacterial hand cleansers and is trying to decide which one to buy. One is a "waterless" hand gel containing 70% isopropanol, the second is an "antibacterial" hand soap containing triclosan (a phenolic), and the third is a
wipe that lists benzethonium chloride (a synthetic quaternary ammonium salt) as the active ingredient. Compare and contrast these cleansers in terms of the action of the antimicrobial ingredient and the level of disinfection (degerming, germistatic, germicidal).
What will be an ideal response?
All three are germicidal, although not all to the same degree. The alcohol of the waterless hand cleaner is a germicide that disrupts cytoplasmic membranes and denatures proteins. It is not effective against bacterial endospores or fungal spores, and it has limited effect on nonenveloped viruses. The alcohol evaporates quickly, so the germicidal effect is short term. The waterless hand cleaner is an intermediate-level disinfectant and is not an effective degermer. The hand soap contains a phenolic, which also damages cytoplasmic membranes and denatures proteins, and is effective on the same range of microbes as the alcohol. Phenolics are intermediate-level disinfectants that persist on surfaces for long periods of time, providing extended disinfection. If used with running water and the hands are vigorously rubbed, the hand soap can be an effective degermer. Synthetic "quats" (quaternary ammonium compounds) disrupt cell membranes. They are effective against fungi, enveloped viruses, and most bacteria, but not against nonenveloped viruses, nor on endospores. Quats are low-level disinfectants that are germicidal for some microbes. The action of using and discarding the wipe provides some degerming effect.
Bloom's Taxonomy: Analysis
Section: Chemical Methods of Microbial Control
Learning Outcome: 9.19
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