According to scientists a simple hand-held torch-like device can swiftly kill dangerous bacteria, offering a potential boon for emergency workers battling infection risks in wars or disaster zones. The device was created by an international team of researchers from China's Huazhong University of Science and Technology, Australia's CSIRO Materials Science and Engineering, the University of Sydney and the City University of Hong Kong.
The “plasma flashlight” delivers a charged, or ionized, jet of gas to zap germs, a team of researchers in China, Australia and Hong Kong said in their study. Hot plasma sterilizers are already used to disinfect surgical instruments, but they are expensive, refrigerator-sized devices that operate at high temperatures. Sterilizers that operate at cooler temperatures require external power such as a wall electrical supply or a generator, as well as a gas feed, in order to keep working. But the new device is driven by a 12-volt battery and does not need a gas feed, according to the study. The study appears in a British publication, the Journal of Physics D: Applied Physics.
According to the inventors they tested it on a thick mat or biofilm of up to 17 layers of Enterococcus faecalis, a germ that is resistant to heat treatment and antibiotics, sometimes causing infections in dental surgery. Biofilm is formed by bacteria to resist treatment and is very difficult to kill, even with intense heat, Prof Ostrikov said. “That's why alternative approaches like this plasma are sought after,” Prof Ostrikov told AAP. In the experiment, five minutes of exposure to the plasma ray burned through 25 micrometres of 17 different layers of bacteria. The plasma not only inactivated the top layer of cells, but penetrated deep into the very bottom layers to kill the bacteria.
“In this study, we chose an extreme example to demonstrate that the plasma flashlight can be very effective even at room temperature,” said Ken Ostrikov, from the Plasma Nanoscience Centre in Australia. “For individual bacteria, the inactivation time could be just tens of seconds.” The plasma in the experiments was measured at between 20 degrees C and 23 degrees C, which means it is close to room temperature and does not burn the skin.
Ostrikov said that the flash gun might need to be made a bit smaller and redesigned to make it more useful in the field, but it would have obvious benefits for killing bacteria in medical emergencies, for operations in far-flung places or in warzones and natural disaster sites. With technical modifications and economies of scale, the device could be made for less than $100, Prof Ostrikov said.
The reason behind its effectiveness is unclear. It could be that there is a reaction between the plasma and the surrounding area which creates types of oxygen molecules to which E. faecalis germs are especially vulnerable say researchers.
Last year, the Max Planck Institute for Extra-terrestrial Physics in Germany said a similar flashlight-shaped device, tested in a laboratory, destroyed samples of a notorious food bug - the O104:H4 strain of Escherichia coli.