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SKEPTOID BLOG:

Hand-washing with Triclosan: Are We Getting Whitewashed?

by Stephen Propatier

June 5, 2014

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Antimicrobial additives have become ubiquitous in consumer products. Their health benefits are at best questionable. Skeptoid has done a brief treatise about this subject in Episode #148, related to antibacterial soap. Since that episode more evidence about the most common additive, triclosan, continues to cause concern. Microbiologists object to the use of antimicrobial additives. They cite growing evidence that bacterial antibiotic resistance is developing from exposure to triclosan. This is unexpected since tricolsan's chemical activity is distinctly different from most antibiotics.

Triclosan is used as a antimicrobial agent in hundreds of common commercial products. What are the risks to using triclosan-containing products and what are the benefits? Let's critically analyse the reasons for the additive and what impact, if any, it has on the spread of infectious disease.

Triclosan is a phenylether, or chlorinated bisphenol, with a broad-spectrum antimicrobial action that is designated as a Class III drug by the Food and Drug Administration. (Class III drugs are compounds with high solubility and low permeability.) Triclosan works by blocking the active site of the enoyl-acyl carrier protein reductase enzyme (ENR), which is an essential enzyme in fatty acid synthesis in bacteria. By blocking the active site, triclosan inhibits the enzyme, and therefore prevents the bacteria from synthesizing fatty acid, which is necessary for building cell membranes and for reproducing. Since humans do not have this ENR enzyme, triclosan has long been thought to be fairly harmless to us. Triclosan is a very potent inhibitor, and only a small amount is needed for powerful antibacterial action.

Triclosan has a broad range of activity that encompasses many, but not all, types of Gram-positive and Gram-negative non-sporulating bacteria, some fungi, Plasmodium falciparum, and Toxoplasma gondii. It is bacteriostatic (it stops the growth of microorganisms) at low concentrations, but higher concentrations are bactericidal (it kills microorganisms). The organisms most sensitive to triclosan are staphylococci, some streptococci, some mycobacteria, Escherichia coli, and Proteus (against which triclosan is effective at concentrations that range from 0.01 mg/L to 0.1 mg/L). Methicillin-resistant Staphylococcus aureus (MRSA) strains are also sensitive to triclosan and may or may not have an increased resistance to triclosan (it is sensitive to concentrations of triclosan in the range of of 0.1—2 mg/L). Enterococci are much less susceptible than staphylococci, and Pseudomonas aeruginosa is highly resistant.

Triclosan has been used since 1972, and is now found in the following products:

?soaps
?hand-washes
?dishwashing products
?laundry detergents and softeners
?plastics (e.g. toys, cutting boards, kitchen utensils)
?toothpaste and mouthwashes
?deodorants and antiperspirants
?cosmetics and shaving creams
?acne treatment products
?hair conditioners
?bedding
?trash bags
?apparel, such as socks and undershirts
?hot tubs, plastic lawn furniture
?impregnated sponges
?surgical scrubs
?implantable medical devices
?pesticides


At this time, in the United States, manufacturers of products containing triclosan must say so somewhere on the label. Triclosan is used as a built-in antimicrobial product protection, under the trade name of Microban, in antimicrobial solutions for consumer, industrial, and medical products around the world. The Microban technology is engineered into a breadth of materials, including polymers, textiles, coatings, ceramics, paper and adhesives.

Antimicrobial additives sound beneficial from a disease-prevention standpoint. There is clear financial benefit to antimicrobial labels for the manufacturer. Consumers will buy products at higher cost for the perceived benefit of reduced pathogenic organisms on skin, clothing, or surfaces. It sounds like a traditional win-win scenario; but is it?

The use of antimicrobial/antibacterial additives in soaps and cleansers promotes the idea that these products are killing "germs." Most lay persons interpret this to mean pathogens, or disease-causing microbes. Most people understand that physically cleaning removes microbes. The common misconception is that the addition of an agent that "kills" them makes a cleaning product safer/better. Also, some believe that normal soaps and cleansers do not remove bacteria unless it has a antimicrobial additive. This is not actually true. Unless you are utilizing a powerful bactericidal chemical like sodium hypochlorite solution (bleach), the action of scrubbing and rinsing has a greater effect. The additive mostly has a mild bacteriostatic effect.

In conventional soaps and detergents triclosan is unlikely to significantly reduce the risk of pathogenic infection. Worse, this could potentially create a false sense of security and cause the user to relax other efforts to keep surfaces clean. It may minimize the time and effort people put into hand-washing. It may give people with poor understanding the misconception that they are sterilizing a surface, dish, or their hands. Lack of understanding about microbes and good marketing is a dangerous combination for health prevention. In truth, human behavior, bacterial evolution, negate the perceived benefits of triclosan. Additionally, there is mounting evidence of a direct negative consequence due to broad low level overuse.

Triclosan is an effective antimicrobial treatment at the 2% concentration range. Research has demonstrated that cleaning with a soap containing 2% triclosan prior to surgery lowers a patient's risk for postoperative infection. MRSA infection risk is significantly lowered with 2% wash. A 2% concentration is good for a preoperative preparation, but you wouldn't want to use that concentration for daily washing. That concentration would be an irritant and possibly toxic with regular use. Most hand soaps have a 0.15% concentration. Unfortunately, at that level there is no the evidence for reducing presence of pathogenic organisms. There is evidence that it is disruptive to our natural skin flora which may reduce the skin's benefit as the primary barrier to pathogens..

The objections to triclosan in products are longstanding, and a frequently debated issue. New concerns are evolving from independent lines of evidence relating triclosan use to antibiotic resistance.

Since the 1990s there has been a steady stream of laboratory-based studies showing a link between triclosan exposure and worsening antibiotic resistance. E. Coli colonies and Psuedomonas colonies seemed to develop greater resistance to antibiotics after serial exposure to triclosan. The mechanism for this is unclear since triclosan doesn't use the same mechanism of action that antibiotics do. Recently, the same effect has been found in salmonella bacteria. There is also bacteria-to-bacteria transmission of this resistance, meaning that beneficial organisms are constantly exposed to triclosan and that may impart a resistance to antibiotics. In turn "good" bacteria can share that information through plasmids, giving away the resistance to pathogens. Triclosan-induced enhanced antibiotic resistance may be occurring.

Not everyone is convinced about the claim of antibiotic resistance from triclosan. Laboratory findings do not always translate to real world issues. Previous research has shown that the highly adaptable MRSA organism doesn't seem to gain antibiotic resistance from exposure to triclosan. Microbiologists have argued that this is due to the fact that MRSA is already resistant to most antibiotics.

In my opinion, there are several lines of evidence supporting the antibiotic resistance hypothesis. One is a sort of natural selection for hardier organisms: it may be that the organism is adapting a barrier against the bacteriocide, that barrier may also block antibiotics. The mechanism, although plausible, is unclear at this time.

We need to stop putting this additive in soaps just so the uninformed will buy them. It will not keep you from getting sick any better than just plain soap and water. It may encourage a false sense of security and poor hygiene habits. It may be teaching the pathogens how to defeat our best drugs. Bacteria have been around longer than any other creature. They live in radiation, partial-pressure vacuums, temperature extremes, and environments deadly to us. It is unlikely that a very small concentration of a substance slightly toxic to them will provide any lasting benefit. Evolution of bacteria shows time and time again that they quickly overcome every obstacle.

The overwhelming scientific evidence indicates that everyday soaps and cleansers with small concentrations of bacteriocidal chemicals are not helpful and may in fact be harmful. Don't buy them; you don't need them. It is more important to spend proper time and technique washing rather than paying for some 0.15% chemical additive.

References:


  1. Leahy, C. (2014, May 5). Back with a Vengeance: The Trouble with Defeating Diseases. Know. Retrieved June 5, 2014, from http://www.utexas.edu/know/2014/05/05/back-with-a-vengeance-the-trouble-with-defeating-diseases/

  2. Triclosan Material Safety Data Sheet. (n.d.). Retrieved June 5, 2014, from http://wirud-ingredients.com/certificates/subs/8_1.html

  3. Rodrigues, D., Teixeira, P., Oliveira, R., & Azeredo, J. (2011, January 1). Salmonella enterica Enteritidis Biofilm Formation and Viability on Regular and Triclosan-Impregnated Bench Cover Materials. Journal of Food Protection, Number 1, January 2011: 32-37. Retrieved June 5, 2014, from http://www.ingentaconnect.com/content/iafp/jfp/2011

  4. Courtney, K.D., Moore, J.A. Teratology studies with 2,4,5-T and 2,3,7,8-TCDD. Toxicology and Applied Pharmacology, Vol. 20: 396.

  5. Russell, A. D. (2003). Similarities and differences in the responses of microorganisms to biocides. Journal of Antimicrobial Chemotherapy, No. 52: 750—63.

  6. Levy, C. W., Roujeinikova, A., Sedelnikova, S. et al. (1999). Molecular basis of triclosan activity. Nature, No. 398: 383—4.

  7. Triclosan: White Paper prepared by The Alliance for the Prudent Use of Antibiotics (2011). Retrieved June 5, 2014, from http://www.tufts.edu/med/apua/consumers/personal_home_21_4240495089.pdf

  8. Mikulov, M., and Biroov, L. (2008, December 12). Development of triclosan and antibiotic resistance in Salmonella enterica serovar Typhimurium. Journal of Medical Microbiology, Vol. 58, No. 4: 436-91. Retrieved June 5, 2014, from http://jmm.sgmjournals.org/content/58/4/436.short

by Stephen Propatier

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