Triclosan (sometimes abbreviated as TCS) is an antibacterial and antifungal agent present in some consumer products, including toothpaste, soaps, detergents, toys, and surgical cleaning treatments. It is similar in its uses and mechanism of action to triclocarban. Its efficacy as an antimicrobial agent, the risk of antimicrobial resistance, and its possible role in disrupted hormonal development remains controversial. Additional research seeks to understand its potential effects on organisms and environmental health. Triclosan was developed in 1966. A 2006 study recommended showering with 2% triclosan as a regimen in surgical units to rid patients' skin of methicillin-resistant Staphylococcus aureus (MRSA).
Uses Triclosan was used as a hospital scrub in the 1970s. Prior to its change in regulatory status in the EU and US, it had expanded commercially and was a common ingredient in soaps (0.10–1.00%), shampoos, deodorants, toothpastes, mouthwashes, cleaning supplies, and pesticides. It also was part of consumer products, including kitchen utensils, toys, bedding, socks, and trash bags. Triclosan was registered as a pesticide in 1969. US EPA registration numbers are required for all EPA-registered pesticides. As of 2017, there were five registrations for triclosan with the EPA. Currently, there are 20 antimicrobial registrations with the EPA under the regulations of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The antimicrobial active ingredient is added to a variety of products where it acts to slow or stop the growth of bacteria, fungi, and mildew. In commercial, institutional, and industrial equipment uses, triclosan is incorporated in conveyor belts, fire hoses, dye bath vats, or ice-making equipment as an antimicrobial. Triclosan may be directly applied to commercial HVAC coils, where it prevents microbial growth that contributes to product degradation. In the United States, by 2000, triclosan and triclocarban (TCC) could be found in 75% of liquid soaps and 29% of bar soaps, and as of 2014 triclosan was used in more than 2,000 consumer products. In healthcare, triclosan is used in surgical scrubs and hand washes. Use in surgical units is effective with a minimum contact time of approximately two minutes. More recently, showering with 2% triclosan has become a recommended regimen in surgical units for the decolonization of patients whose skin carries methicillin-resistant Staphylococcus aureus (MRSA). Two small uncontrolled case studies reported the use of triclosan correlated with reduction in MRSA infections. Triclosan is also used in the coatings for some surgical sutures. There is good evidence these triclosan-coated sutures reduce the risk of surgical site infection. The World Health Organization, the American College of Surgeons and the Surgical Infection Society point out the benefit of triclosan-coated sutures in reducing the risk for surgical site infection. Triclosan has been employed as a selective agent in molecular cloning. A bacterial host transformed by a plasmid harboring a triclosan-resistant mutant FabI gene (mFabI) as a selectable marker can grow in presence of high dose of triclosan in growth media.
Effectiveness In surgery, triclosan coated sutures reduce the risk of surgical site infection. Some studies suggest that antimicrobial hand soaps containing triclosan provide a slightly greater bacterial reduction on the hands compared to plain soap. As of 2013, the US FDA had found clear benefit to health for some consumer products containing triclosan, but not in others; for example the FDA had no evidence that triclosan in antibacterial soaps and body washes provides any benefit over washing with regular soap and water. A Cochrane review of 30 studies concluded that triclosan/copolymer-containing toothpastes produced a 22% reduction in both dental plaque and gingival inflammation when compared with fluoride toothpastes without triclosan/copolymer. There was weak evidence of a reduction in tooth cavities, and no evidence of reduction in periodontitis. A study of triclosan toothpastes did not find any evidence that it causes an increase in serious adverse cardiac events such as heart attacks. A study by Colgate-Palmolive found a significant reduction in gingivitis, bleeding, and plaque with the use of triclosan-containing toothpaste. An independent review by the Cochrane group suggests that the reduction in gingivitis, bleeding, and plaque is statistically significant (unlikely to occur by chance) but not clinically significant (unlikely to provide noticeable effects). Triclosan is used in food storage containers although this use is banned in the European Union since 2010. Veterinary use as a biocidal product in the EU is governed by the Biocidal Products Directive.
Chemical structure and properties This organic compound is a white powdered solid with a slight aromatic, phenolic odor. Categorized as a polychloro phenoxy phenol, triclosan is a chlorinated aromatic compound that has functional groups representative of both ethers and phenols. Phenols often demonstrate antibacterial properties. Triclosan is soluble in ethanol, methanol, diethyl ether, and strongly basic solutions such as a 1M sodium hydroxide solution, but only slightly soluble in water. Triclosan can be synthesized from 2,4-dichlorophenol.
Synthesis Under a reflux process, 2,4,4'-trichloro-2'-methoxydiphenyl ether is treated with aluminium chloride. The United States Pharmacopeia formulary has published a monograph for triclosan that sets purity standards.
Mechanism of action At high concentrations, triclosan acts as a biocide with multiple cytoplasmic and membrane targets. However, at the lower concentrations seen in commercial products, triclosan appears bacteriostatic, and it targets bacteria primarily by inhibiting fatty acid synthesis. Triclosan binds to bacterial enoyl-acyl carrier protein reductase (ENR) enzyme, which is encoded by the gene fabI. This binding increases the enzyme's affinity for nicotinamide adenine dinucleotide (NAD+). This results in the formation of a stable, ternary complex of ENR-NAD+-triclosan, which is unable to participate in fatty acid synthesis. Fatty acids are necessary for building and reproducing cell membranes. Vertebrates do not have an ENR enzyme and thus are not affected by this mode of action. Triclosan has also been reported to interact with tubulin and inhibit its polymerization.
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