MRSA: An example of an antibiotic-resistant infection. Source: http://en.wikipedia.org/wiki/File:MRSA7820.jpg
On 15 September 2013, scientists at the University of Groningen published their discovery of light-controlled antibiotics in the journal Nature Chemistry. These “switchable” antibiotics can be turned on by ultraviolet light and turned off after a certain amount of time (1).
The antibiotic developed by Ben Feringa’s team at the University of Groningen works by switching between a trans isomer that is harmless to bacteria and a cis isomer that has microbe-killing properties. Exposing the antibiotic to ultraviolet light causes this switch. Left alone, the bacteria-killing cis isomers will slowly convert back to the harmless trans isomers (2).
There are several benefits to having an antibiotic capable of inactivation. Normally, residual active antibiotics in the body would allow bacteria to adapt and develop resistance. Active antibiotics that have left the body and end up in the sewage system, for example, are also a source of bacterial resistance (1).
Bacterial resistance is a growing problem because the number of compounds that can be used effectively as antibiotics is limited; if bacteria become immune to them, bacterial infections will be untreatable. Documented examples of this include MRSA (methicillin-resistant staph infection), which is quite difficult to treat in humans (3).
The light-controlled antibiotics switch off after a half-life of two hours at body temperature, not burdening the environment and not allowing bacteria to develop immunities to it. For this reason, these new antibiotics are a “novel method to combat resistance,” said Stuart Conway, a biological photochemistry scientist at the University of Oxford (2).
The other issue with current antibiotics is that they target all bacteria in the body, even the ones that naturally exist in the gut and assist with the digestive process. As a result, a common side effect of taking antibiotics is diarrhea. Feringa says, “you could take an inactive antibiotic for a skin infection and then activate it at the site where it is required. No useful bacteria in the intestines will be killed this way” (1).
These new antibiotics are also useful in research; researchers can control the growth of bacteria very specifically at a particular place and time. With this antibiotic, researchers can investigate which factors influence the growth of bacteria, the action of the antibiotic, and the origin of their resistance (4).
Moving forward, Feringa’s team seeks to activate the compound with visible or infrared light, both of which are less harmful to humans than ultraviolet radiation. In spite of all the potential benefits of these new antibiotics, the path from the concept to working drug could be as long as a decade (1).
References
1. Chemists Develop Switchable Antibiotic. Available at http://www.sciencedaily.com/releases/2013/09/130916091019.htm (13 Oct 2013).
2. A. Extance, Light-switch antibiotics could undermine resistance. Available at http://www.rsc.org/chemistryworld/2013/09/light-switch-antibiotics-undermine-resistance (13 Oct 2013).
3. MRSA infection. Available at http://www.mayoclinic.org/mrsa/ (13 Oct 2013).
4. W. Velema, et al, Optical control of antibacterial activity. Nature Chemistry (2013) DOI: 10.1038/NCHEM.1750. Available at http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.1750.html (13 Oct 2013).