Triclosan und Antibiotikaresistenz

6. Conclusions of the SCCS

• 6.1 Does triclosan pose a risk, and what are the current gaps in knowledge?
• 6.2 Is it still safe to use triclosan as a preservative in cosmetic products?

6.1 Does triclosan pose a risk, and what are the current gaps in knowledge?

The Scientific Committee on Consumer Safety (SCCS) concludes that at present there are important scientific and technical gaps in knowledge.

Scientific gaps:

1. Environmental studies to measure any resistance and cross-resistance to antibiotics following the use of triclosan.
2. There are some studies that measure whether exposure to relatively low concentrations of triclosan leads to antibiotic resistance. This research should be extended to a much wider range of bacteria.
3. There is evidence from laboratory samples that triclosan could have a role in antibiotic resistance. To determine whether or not these results have any relevance for public health, full epidemiological studies are needed.
4. Bacteria have the capacity to transfer genetic information from one another, and this can in theory lead to the propagation of resistance or virulence. It is not known at present if this process is affected by the presence of Triclosan.

Technical gaps:

1. We need to have standard methods of measuring resistance and cross-resistance.
2. To assess the amount of triclosan that bacteria are exposed to, we need information on the amount of triclosan that is manufactured and used.
3. Triclosan is widespread in the environment but we need to know the actual values much more accurately. To determine whether or not resistance will develop in the environment, we also need to know in more detail which microorganisms come into contact with triclosan, how much of it they take up and whether or not their genetic make up is such that resistance genes could be activated and perhaps transferred to other bacteria.
4. We need methods of measuring the minimum concentration of triclosan that can lead to antibiotic or biocide resistance.
5. Laboratories need to use biofilms rather than single bacterial cells, to assess the efficacy of biocides and there need to be European standards of such tests for healthcare applications.

There are several reasons why the use and release of triclosan into the environment could pose a risk:

• From a genetic point of view, exposing bacteria for short periods of time to concentrations of triclosan that are not high enough to kill them, makes bacteria secrete substances involved in resistance or activates resistance genes in bacteria. Some of these genes are also involved in resistance to different drug families, can move from one bacterium to another and, in principle could be activated in bacteria already present in soils.
• Triclosan, like any other biocide, contributes to the selection of less susceptible bacteria, because it eliminates competition since it wipes out those bacteria that are more susceptible to it. However, the impact of such a selection is unclear.
• Biofilms are widespread in the environment and show increased resistance. They have a tough exterior, a wide range of defence mechanisms and the potential to exchange resistance genes between different species of bacteria that live together as part of a colony.

Triclosan is the most studied biocide with respect to bacterial resistance. However, there is still not enough information to do a full risk analysis. In particular, we need to know the amount of triclosan that bacteria are exposed to in the environment, and how much of this they actually take up. We cannot tell either how much each different type of product contributes to the pool of triclosan found in the environment. Other chemicals that can also affect microorganisms are found together with triclosan so it is difficult to tease out the effects of each biocide separately.

There are no epidemiological data linking exposure to triclosan in cosmetics or other products, and outbreaks of resistant bacteria that are harmful for humans or animals.

When used appropriately, biocides, including triclosan, have an important role to play in disinfection, antisepsis and preservation. Information on the expression/triggering of bacterial resistance mechanisms should be considered to (re-)assess the uses of triclosan in order to preserve its efficacy. More...

6.2 Is it still safe to use triclosan as a preservative in cosmetic products?

To date, there is no evidence that using triclosan leads to an increase in antibiotic resistance. However it is too early to say that triclosan exposure never leads to microbial resistance.

One cannot ignore the hazards identified in laboratory studies so it is important that industry continues investing in research to understand better the role of triclosan on bacterial resistance. The research available was state-of-the-art at the time it was done but modern tools are much more powerful than these so there should be additional studies, particularly on bacteria taken from hospitals or the environment, rather than on isolated samples grown in the laboratory. More...