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Rapid test shows how antibiotics combine to kill bacteria

Dan Andersson Photo Mikael Wallerstedt

Researchers at Uppsala University have developed a new method to rapidly determine how effective two antibiotics combined can be in stopping bacterial growth.

The new method is simple for laboratories to use and can provide greater scope for customizing treatment of bacterial infections, states the researchers. The study is published in PLOS Biology.


With the newly developed method known as CombiANT (combinations of antibiotics), interactions between various antibiotics can be tested on agar plates and results obtained in 24 hours. The lead author of the study, Nikos Fatsis-Kavalopoulos, developed the method at Uppsala University. It is based on creating a “concentration gradient” of antibiotics that have been cast into an agar plate, using a 3D-printed plastic disc. On the agar plate, bacteria that have been isolated from an individual patient are then cultured to see how they react to different combinations of antibiotics.


In their study, the researchers investigated E. coli bacteria isolated from urinary tract infections. Different cultures of E. coli proved not to react in the same way to specific antibiotic combinations. A combination of antibiotics that had synergistic effects on most cultures brought about antagonism in some, with the result that the treatment for the latter group was inferior.

“This result may be of great clinical importance. Consequently, instead of assuming that synergistic and antagonistic interactions are equal for all bacterial isolates, we test individually every isolate taken from an infected patient,” says Dan I. Andersson, Professor of Medical Bacteriology at Uppsala University, who is primarily responsible for the study.

Photo of Dan I. Andersson: Mikael Wallerstedt