Tests determine antibiotic resistance in less than 90 minutes

PULLMAN, Wash. A technique that measures the metabolic activity of bacteria with an electric probe can identify antibiotic resistance in less than 90 minutes, a dramatic improvement from one to two days required by current techniques.

This discovery means that doctors could quickly know which antibiotics will or will not work for a patient’s life-threatening infection, a dilemma that doctors face daily in hospitals around the world. A research team from Washington State University reports on their work in the journal Biosensors and Bioelectronics.

“The idea here is to give physicians results much faster so they can make clinically appropriate decisions within the time frame they work, instead of having to wait,” said Douglas Call, Regents Professor at Paul G. Allen School of Global Health and a co-author of the paper. “Instead of looking for the growth of a culture, we are looking for metabolism, and that is basically what we discover by the movement of these electrons, so that it can happen in a much shorter period of time compared to a conventional culture-based analysis.”

The prevalence of antibiotic resistance is increasing around the world and threatens the ability to treat many common infectious diseases. For example, millions of people in the United States become infected annually with drug-resistant pathogens, and thousands of people die from pneumonia or bloodstream infections that become impossible to treat.

To finally determine if a particular infection is resistant to antibiotics, it requires separating and growing the bacteria in a laboratory and watching the population grow in a process that can take up to two days or more. Doctors facing a sick patient often need to prescribe an antibiotic immediately without having complete information on how well it will work.

A researcher measures the electrochemical signal of bacteria.
In their paper, the WSU team used a probe to directly measure the electrochemical signal from the bacteria

In their paper, the WSU team used a probe to directly measure the bacteria’s electrochemical signal, thereby measuring their metabolism and respiration and learning how they perform long before they would be visible in culture. By looking at eight different bacterial strains, the researchers were able to use the bacteria’s electrical signal to determine in less than 90 minutes which ones were susceptible or resistant to antibiotics.

The bacteria that still metabolize and “breathe” after antibiotic treatment are considered resistant.

Previous attempts to measure the electrochemical activity of bacteria had been limited because most bacterial species are unable to transfer electrons directly to an electrode, said Abdelrhman Mohamed, a postdoc researcher at the Gene and Linda Voiland School of Chemical Engineering and Bioengineering , who was a leader. author on paper. The researchers added a chemical mediator to their assay, which acted as a shuttle that took the electrons from the bacteria’s surface proteins and moved them to the researchers’ electrode, where the electrical signal can be measured.

“It allows us to have a universal mechanism that can test all types of pathogens,” Mohamed said.

The researchers tested four different bacterial species that cause hospital-acquired infections and tested a range of antibiotics that work using different mechanisms. They also developed an antibiotic sensitivity index to categorize the results in a way that could help doctors decide which antibiotic to use.

Researchers now plan to design their probe to be practical and standardized for clinicians to use and hope to commercialize it.

“It’s really exciting to be involved in a project that is not only valuable from a scientific point of view, but is something that has commercial and industrial uses that could potentially one day actually improve people’s lives,” said Gretchen Tibbits, a lead author on paper and graduate. student at Voiland School.

They are also working on better understanding the basic mechanisms of the electrochemical process to further improve it.

“We do it in two hours, but if we understand mechanisms better, we might be able to do it in minutes,” said Haluk Beyenal, co-author of the paper and professor at Voiland School. “As long as the bacteria are alive, we can make this measurement.”

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