Scientists at Washington University School of Medicine in St. Louis have developed an ultrashort-pulse laser that can kill multidrug-resistant bacteria and their spores, and without damaging human cells. The laser works by vibrating and breaking protein structures within the bacterial cell, resulting in biochemical disruption and eventual death. The researchers hope that the technique could prove useful in decontaminating wounds and blood products.
Killing multidrug-resistant bacteria is no mean feat, as many of the common antibiotics we use are no longer effective against them. General antibacterial strategies that could kill such bacteria, such as heat or applying bleach, are fine for decontaminating surfaces and equipment, but are clearly not safe to use within the human body.
These researchers have developed a laser technology that can kill microbes, such as bacteria and viruses, with ease, but does not harm human cells. “The ultrashort-pulse laser technology uniquely inactivates pathogens while preserving human proteins and cells,” said Shaw-Wei Tsen, one of the leaders of the research, in a press release. “Imagine if, prior to closing a surgical wound, we could scan a laser beam across the site and further reduce the chances of infection. I can see this technology being used soon to disinfect biological products in vitro, and even to treat bloodstream infections in the future by putting patients on dialysis and passing the blood through a laser treatment device.”
The technology works by disrupting protein structures in the bacterial cells. Once the proteins break apart, they frequently stick to other cellular components, causing a tangled mess and ultimately leading to the death of the cell. However, at the laser power levels required to kill bacterial cells and viruses, human cells are unaffected.
“We previously published a paper in which we showed that the laser power matters,” said Tsen. “At a certain laser power, we’re inactivating viruses. As you increase the power, you start inactivating bacteria. But it takes even higher power than that, and we’re talking orders of magnitude, to start killing human cells. So there is a therapeutic window where we can tune the laser parameters such that we can kill pathogens without affecting the human cells.”
So far, the researchers have tested the laser on multidrug-resistant bacteria in the lab including MRSA and extended spectrum beta-lactamase-producing E. coli, and demonstrated that 99.9% of the bacterial samples were killed.
“Anything derived from human or animal sources could be contaminated with pathogens,” said Tsen. “We screen all blood products before transfusing them to patients. The problem is that we have to know what we’re screening for. If a new blood-borne virus emerges, like HIV did in the ’70s and ’80s, it could get into the blood supply before we know it. Ultrashort-pulse lasers could be a way to make sure that our blood supply is clear of pathogens both known and unknown.”