Researchers at Washington State University have developed an electrochemical test that can rapidly identify antibiotic-resistant bacteria in patient samples. The technology can provide a result in less than 90 minutes, and is based on measuring the electrochemical activity of the bacteria after they are exposed to antibiotics. The data reveal the metabolism and respiration of the bacteria, and if they are still happily metabolizing after exposure to an antibiotic, then they are considered to be resistant to it. By providing a rapid answer to the question of antibiotic resistance, the method could be very helpful for clinicians in prescribing the most appropriate antibiotic for their patients.
In the age of antibiotic-resistant bacteria, prescribing the correct antibiotic is becoming critical. If a clinician gets it wrong, the treatment won’t work, and misused antibiotics could even contribute to new resistant forms of bacteria. At present, the most common way for healthcare staff to determine the resistance status of an infection is to take a sample from the patient and then analyze it in the lab. However, this involves culturing the bacteria for significant periods of time, perhaps as long as a couple of days. For a patient with a serious infection, this is too long.
“The idea here is to give the doctors results much more quickly so that they can make clinically appropriate decisions within that timeframe that they’re working, rather than having to wait,” said Douglas Call, a researcher involved in the study. “Instead of looking for growth of a culture, we look for metabolism, and that is basically what we’re detecting by the movement of these electrons so it can happen in much shorter time spans compared to a conventional culture-based assay.”
The new test involves using a probe to measure the electrochemical activity of the bacteria, as an indirect measurement of their metabolism. The test involves exposing the bacterial sample to an antibiotic, and then measuring the metabolism of the bacteria – if they continue to metabolize at normal levels, then they are likely to be largely unaffected by the drug.
Previously, this would have been very difficult, as bacteria do not readily transfer electrons to an electrode in their growing medium, but the researchers used a work-around in the form of a chemical addition that can shuttle electrons from the surface of the bacterium to the electrode.
Excitingly, the researchers may be able to speed the test up further, with additional development. “We are doing it in two hours, but if we understand mechanisms better, maybe we can do this in minutes,” said Haluk Beyenal, another of the developers of the new test. “As long as the bacteria are alive, we can do this measurement.”
Study in Biosensors and Bioelectronics: Rapid differentiation of antibiotic-susceptible and -resistant bacteria through mediated extracellular electron transfer