When a patient suffers from a serious infection, doctors are in a race against time to find the best antibiotic treatment. The traditional Petri dish method requires at least 8 hours for analysis, and sometimes takes up to 24 hours.
Observing bacteria’s oxidative stress
In collaboration with LTM*, two CEA teams (Leti and Irig) created an “optical tweezer” for bacteria that could carry out the same analysis in only two hours. Thanks to a new paradigm, the results would be not only quicker, but also just as reliable.
Pierre Marcoux, an engineer and researcher at CEA-Leti, explains: “Treating bacteria with an antibiotic and waiting to see if it continues to grow is a very slow process. Instead, we focus on observing a bacteria’s oxidative stress. If the bacteria is sensitive to a treatment, its membrane will rapidly become charged with reactive oxygen species.”
Almost instantaneous detection
How can researchers detect this change in oxidative stress? The “optical tweezers” use two micro-mirrors that reflect a laser beam thousands of times. This creates a force that attracts nearby bacteria. Depending on whether they are healthy or oxidized, these bacteria will have a different, measurable impact on the laser’s frequency. While the detection process is almost instantaneous, it must be repeated multiple times to ensure reliability. As a result, the overall process takes around two hours.
Creating an easy-to-use device
The device has already proven its worth when used on bacteria at higher and higher temperatures. The next step is to improve and evaluate the process with bacteria that receive an antibiotic treatment. The SUPPLY research project is a French and Swiss collaboration amongst CEA, LTM, EPFL** and the University Hospital of Lausanne. The goal is to create a lab prototype in four years’ time.
“We have to validate our paradigm by evaluating whether or not the observation of oxidative stress is as reliable as a Petri dish culture. In parallel, we will develop an easy-to-use device that will be practical for biologists,” concludes Pierre Marcoux.
An opportunity to reduce antibiotic resistance
SUPPLY will also study another “optical tweezer” designed by researchers at EPFL. The project is being closely follow by clinical practitioners who, for the past 20 years, have been calling for more efficient tools to implement antibiotic treatments. With the current Petri dish method, doctors must give broad-spectrum antibiotics while waiting for test results. This situation increases the risk of antibiotic resistance without necessarily alleviating the patient’s condition.
*LTM: Laboratoire des technologies de la microélectronique (Grenoble)
**EPFL : École polytechnique fédérale de Lausanne