Antibiotics are one of the most important scientific discoveries in the 20th century, but their usefulness is rapidly fading away. Overuse leads to drug resistance in bacteria, which may lead us to a future where once simple infections once again threaten our lives. Now Purdue University researchers have found that blue light can weaken a particularly unpleasant "superbug" and make it subject to mild fungicides again.
Staphylococcus aureus is a common bacteria, most of which are harmless, but some strains cause more problems. Methicillin-resistant Staphylococcus aureus (MRSA) is a particularly troublesome bacterium that is most dangerous to people whose immune system has been damaged, which means that it can cause serious infections in hospitals and nursing homes. Unfortunately, this has become increasingly difficult to treat - not only is it resistant to methicillin, but also to an increasing number of other common antibiotics.
New antibiotics are still being developed, but eventually bacteria inevitably develop resistance. So scientists are trying to find long-term solutions that superbacteria cannot adapt, such as antimicrobial materials that can quickly kill bacteria or photosensitive nanoparticles that can release reactive oxygen species to kill superbacteria.
Similarly, Purdue University researchers have developed their own phototherapy. The team found that MRSA could be weakened by "photobleaching" - radically eliminating the colour of bacteria by exposing them to blue light. Because these pigments are part of how bacteria infect their hosts, this may reduce their ability to cause harm.
"When you bleach something in a washing machine, you use chemicals to remove color," says Mohamed Seleem, author of the study. "We're doing very similar things here, but we're using blue light."
Light itself does not kill MRSA - on the contrary, it reduces its defensive capacity enough for drugs and other molecules to complete it, even though bacteria usually resist them. In tests on mice infected with MRSA wounds, researchers found that mild fungicides such as hydrogen peroxide could effectively destroy bacteria weakened by blue light.
The team has been patented to use the device to treat wounds infected by MRSA. The idea is that it will take the shape of a small box with lights and shine through a hole into the wound. Importantly, scientists have found that light is safe in mammalian cells.
"This new tool can treat any surface wound infected with MRSA, which is usually difficult to treat," Seleem said. "The device itself is very compact and easy to use. We hope that in the next few years, anyone can carry it with them."
The study was published in Advanced Science.