This article was first published by The Times of Israel and was re-posted with permission.
Pathogens developing resistance to antibiotics are among the gravest threats to modern medicine, according to the World Health Organization; but new research may have found a way to help doctors fight such germs.
Researchers at The Hebrew University of Jerusalem say they have found a simple method for measuring a bacteria’s tolerance, or the time it takes to kill a bacterial population. This will enable clinicians to more effectively treat strains that are on their path to becoming resistant, the researchers say.
This tolerance has been “largely overlooked in the clinical setting,” according to Nathalie Balaban, the study’s senior author. The protocol exposes a sample population of a bacteria to different concentrations of antibiotics for varied time periods to see how many survive and for how long.
“Routinely measuring tolerance could supply valuable information about the duration of antibiotic treatments, reducing the chance of both under- and over-treatment,” Balaban said. “Furthermore, data compiled from such measurements could give an estimate of how widespread the phenomenon of tolerance really is, which is currently a complete unknown.”
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Currently, doctors test for bacterial resistance, which is an active quality, to decide which antibiotic and dosage to prescribe a patient. The new method, called MDK99, or the minimum duration for killing 99 percent of the population, measures a different quality — bacterial tolerance, which is inactive. Instead of fighting the drug, these bacteria sleep through its presence, only dying when they wake up. If any survive, they can quickly replenish once treatment has stopped. By measuring tolerance, doctors can better decide which antibiotic to administer to kill all of the bacteria.
Resistant strains continue to grow despite exposure to high drug concentrations, while tolerant strains can survive lethal concentrations of an antibiotic for a long period of time before succumbing to its effects. Tolerance is more common than resistance, as it is found in any bacteria population. It is often associated with treatment failure and relapse, and is considered a steppingstone toward the evolution of antibiotic resistance. But unlike resistance, tolerance is poorly understood and is currently not evaluated in healthcare settings.
“The lack of a quantitative measure means that this aspect of the treatment relies largely on the experience of the individual physician or the community,” said Asher Brauner, the study’s first author and a PhD student in Balaban’s lab.
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