A new test reveals which antibiotics truly kill bacteria
Antibiotics are often judged by how well they slow or stop bacterial growth in laboratory tests. What is even
Antibiotics are often judged by how well they slow or stop bacterial growth in laboratory tests. What is even more important, though, is whether those drugs actually kill bacteria inside the human body. Researchers at the University of Basel have now introduced a new way to measure how effectively antibiotics eliminate bacteria, not just suppress them.
This distinction has become critical as antibiotic resistance continues to spread. Resistant bacteria represent one of today’s most serious global health threats. Through genetic mutations, many bacteria are becoming less responsive to commonly used drugs, making infections harder to treat and more likely to persist.
Dormant Bacteria and Lingering Infections
Even bacteria that are not resistant can sometimes survive antibiotic treatment. This often happens when bacteria enter a dormant state. In this condition, they stop multiplying, but antibiotics may fail to kill them. Once treatment ends, these dormant bacteria can become active again and restart the infection.
This challenge is especially severe in diseases such as tuberculosis and other complex infections that require many months of therapy. In such cases, choosing drugs that fully eliminate bacteria and completely clear the infection is essential.
A New Way to Predict Treatment Success
Traditional laboratory tests mainly show whether a drug prevents bacteria from growing, rather than confirming whether the bacteria are dead. To overcome this limitation, researchers led by Dr. Lucas Boeck from the Department of Biomedicine at the University of Basel and University Hospital Basel developed a new testing method designed to better predict real world treatment outcomes. Their findings were published in the scientific journal Nature Microbiology.
The new approach, known as “antimicrobial single-cell testing,” uses advanced microscopy to observe millions of individual bacteria across thousands of different test conditions. “We use it to film each individual bacterium over several days and observe whether and how quickly a drug actually kills it,” explains Lucas Boeck.
This technique allows researchers to determine exactly how many bacteria are eliminated by a treatment and how efficiently that elimination occurs across an entire bacterial population.
To demonstrate the method, the team tested 65 different drug combinations against Mycobacterium tuberculosis, the bacterium responsible for tuberculosis. They also applied the approach to bacterial samples from 400 patients with another severe lung infection caused by Mycobacterium abscessus, a close relative of the tuberculosis pathogen.
Why Some Bacteria Outlast Antibiotics
The researchers observed clear differences between drug combinations, as well as differences between bacterial strains from different patients. Specialists refer to this second factor as antibiotic tolerance. Further analysis showed that specific genetic traits influence how well bacteria can endure treatment and effectively wait it out.
“The better bacteria tolerate an antibiotic, the lower the chances of therapeutic success are for the patients,” says Lucas Boeck. When compared with results from clinical studies and animal models, the new testing method closely matched how well various treatments actually cleared infections.
Benefits for Patients and Drug Development
So far, antimicrobial single-cell testing has mainly been used in research settings, but it could eventually be applied in hospitals and the pharmaceutical industry. According to Boeck, the method could help doctors select antibiotic therapies that are better matched to the specific bacterial strain infecting each patient.
“Our test method allows us to tailor antibiotic therapies specifically to the bacterial strains in individual patients.” He adds that a deeper understanding of the genetic factors behind antibiotic tolerance could lead to faster and simpler testing methods and improve predictions about how effective new antibiotics will be during development.
“Last but not least, the data can help researchers to better understand the survival strategies of pathogens and thus lay the foundation for new, more effective therapeutic approaches,” says Boeck.
