Project Title:
The Dirt on Soap

Group No.:

22

Group Name:

MU AU-MEMBERS

News URL:

http://www.thetimesherald.com/news/stories/20030314/localnews/1175441.html

Author:

Bill Chapin

News Paper:

The Times Herald

Area Key Word:

Triclosan, Antibacterial, Resistance, Disinfectants, Soap

Chemistry Key Word:

Ethers, Hydrogen Bonding, Triclosan

Editorial Comment:



Triclosan(5-Chloro-2-(2,4-dichlorophenoxy)phenol) is a diphenyl ether (Carey chapter 16), and is literally found everywhere: in soaps, deodorants, household cleaners, and even children's toys. America's obsession with sterilization may, however, have been leading to a rise in antibacterial resistant strains of many common bacteria. Doctors and scientists once thought that triclosan, produced in the United States by Ciba Specialty Chemicals, was such a powerful disinfectant because it did not target just one specific enzyme or protein. However, a study cited in Science News proved that this is not true, and that in fact, triclosan works by targeting the enoyl-acyl carrier protein reductase, an enzyme involved in fatty acid synthesis. Figure 3 in the article: Structural basis and mechanism of enoyl reductase inhibition by triclosan. (Stewart, M.J., Parikh, S., Xiao, G., Tonge, P.J., and Kisker, C.. J. Mol. Bio. 1999. 290, 859-865). depicts one of the proposed mechanisms of triclosan action, which is too complex to model without more information about the other molecules involved in the reaction. In the mechanism, the ether and hydroxyl functional groups of triclosan form hydrogen bonds with a hydroxyl group of NADH. Hydrogen bonding and hydrophilic interactions between molecules help to stabilize the triclosan-NADH complex. With the new knowledge of triclosan's mechanism of action against bacteria, some scientist fear that its overuse may contribute to an increase in resistant bacteria.

Since it can be shown that certain mutations in bacterial amino acids do in fact lead to triclosan resistance, the next logical question is whether or not the chemical is worth producing. It is necessary at this point to question of the advantages of using antibacterial products. In a study performed by the National Institute of Health it was found that there was no advantage of using antibacterial soap versus regular soap for one year. Dr. Richard Anderson also argues in "The dirt on soap" article that using antibacterial soaps is not good: he states that some bacteria are healthy, and that simply washing your hands is more important than washing with an antibacterial soap. (To understand more about how washing your hands works, check out the "How Stuff Works" page).

With only early testing, those in the science world do not even agree on the threat of antibacterial strains arising from the overuse of triclosan. In fact, some feel that there is not enough evidence yet to halt their usage. The Soap and Detergent Association for instance, feels that the study performed by Tufts University, which is published in Nature magazine does not prove that triclosan use is promoting bacterial resistance. Instead, they attribute the rise of resistant bacteria to the overuse of antibiotics. The SDA feels that the use of antibacterial soaps has been safe for the past 30 years and that its use should not be discontinued.

Now, as consumers, we must use our new knowledge and understanding to make an informed decision as to whether we feel triclosan is needed in our homes, and if it may pose as a risk in the future.

Question 1:

(ICR) List six products that have the anit-bacterial agent, triclosan, in them.

Answer 1:

Toothpastes, cutting boards, baby toys, deodorants, cosmetics and cooking utensils.

Question 2:

(SCL) How does soap work on a chemical level?

Answer 2:

According to "How Stuff Works", soap molecules have both hydrophilic and hydrophobic ends. The hydrophobic parts of the soap molecule are able to adhere to other hydrophobic particles, including the dirt on the substance being cleaned. The soap's hydrophobic ends encapsulate the dirt, and the hydrophilic ends allow it to be washed away by water.

Question 3:

(EVL) Describe two ways in which the triclosan-NADH complex is stablized.

Answer 3:

Triclosan is hydrogen bound to NADH. Other proteins and enzymes have hydrophobic interactions.

Question 4:

(ICR) What is the primary use of triclosan and what is the main method of killing bacteria?

Answer 4:

Triclosan is a diphenyl ether that is added to many products for its use as a bacteria-killing agent. It kills these bacteria, according to a study in Science News , by inhibiting an enzyme involved in fatty acid synthesis.

Question 5:

(PSP) Now that we have presented you with the facts about triclosan, do you feel that there is enough risk to stop production of antibacterial products? Do you feel that antibacterial detergents are needed, or do you think that general good hygiene practices are enough? Is it necessary to produce plastic toys, cooking utensils and other items that contain triclosan in them, or is this going overboard with antibacterial products. If given the choice between antibacterial soap and soap without this added feature, which would you choose? Do you feel that being antibacterial makes a product more marketable?

Answer 5:

Looking through the articles concerning the over-usage of triclosan, I have noticed many mixed feelings on the risks involved in bacterial resistance. Many newspaper and magazines described the problem in a very pessimistic view, as if the problem with bacteria becoming resistant to triclosan is an issue we need to deal with immediately. However, after reading over study results in scientific magazines and journals, I do not feel the need to stop using antibacterial products, at least not immediately. Although I don't believe that the continuous use of triclosan is causing any great threat on bacterial resistance, I feel that there is no need for the bacteria fighting agent to be added to almost every household item. The fact that studies have proven there is often no benefit in using "antibacterial" products versus products without this label shows there is no need for antibacterial detergents as well. If given the choice between a regular soap and an antibacterial soap, I would definitely choose the regular marked item. The effectiveness of antibacterial soaps has proven to be trivial in every day use. The label of "antibacterial" is simply a marketable ploy to reel consumers into buying the supposed best product. The addition of triclosan to such items as children's toys and kitchen utensils has become ridiculous as well. The constant use of triclosan in everything around the house could possibly slow the effectiveness of triclosan, which is not a great health threat at home, however in a hospital situation, the antibacterial substance's quick response is critical. Overall, I believe that people need to become more aware of what they purchase and how effective the claims on items are in reality. As of now, there has been no clear cut evidence that triclosan does cause any sort of bacterial resistance. However, if the constant overuse of the chemical substance continues, there could possibly be problems. These problems do not simply effect the home, but also hospitals and healthcare facilities that rely on the quick strong acting antibacterial microbe.

©2004 Dr. Rainer Glaser's group