Researchers at the Francis Crick Institute and the University of Western Australia have developed a new imaging method to see where antibiotics have reached bacteria within tissues. The method could be used to help develop more effective antibiotic treatments, reducing the risk of antibiotic resistance.

Bacteria enter human cells during such infections as tuberculosis, causing a challenge for treatment because antibiotics must enter all infected cells in order to be effective. If researchers could develop more effective antibiotics based on where they reach, this could reduce the length of treatment needed, which in turn could reduce the risk of antibiotic resistance developing.

The researchers developed a new imaging method to see where – in infected tissues and in cells – an antibiotic given to treat tuberculosis reaches the bacteria. The scientists are continuing to work on the method, adapting it for other types of antibiotic and to image multiple antibiotics at the same time.

Max Gutierrez at the Crick Institute says: “In the case of tuberculosis, people need to be treated with at least three different antibiotics over six months. We don’t yet fully understand why this extended treatment is needed. We hope that being able to more clearly see where antibiotics are going, will help us better understand this process and find ways to improve it.”

To develop the imaging method, the researcher analyzed lung tissue from mice infected with tuberculosis and treated with the antibiotic bedaquiline. They combined a variety of imaging methods, including confocal laser scanning microscopy, 3D fluorescence microscopy, electron microscopy, and nanoscale secondary ion mass spectrometry, to develop their new approach.

Using this method, they found that bedaquiline had not reached all infected cells in the lung tissue and also had not entered all infected areas within infected cells. They also found this antibiotic was collecting in macrophages and polymorphonuclear cells, both types of immune cells. This was a surprise as these cells have different environments and it wasn’t thought that one antibiotic would be able to enter both.