Scientists Win a Game of Bacterial Hide-And-Seek

When infection strikes, antibiotics are the go-to solution to help patients regain control from the invading bacterial pathogens. However, antibacterial drugs aren’t always 100 percent protective—even after getting better, some patients end up experiencing an infection relapse down the line.

Scientists have been trying to figure out infectious bacteria’s survival strategy: how do these microorganisms escape antibiotic therapies and immune attacks, only to reemerge when the coast is clear?

Dirk Bumann and colleagues at the University of Basel say the question isn’t so much ‘how’ as ‘where’. The team discovered that bacteria such as Salmonella have safe zones in the body where they can remain hidden.

According to Bumann, one in every 100 bacteria survives after a course of antibiotics. The challenge is finding their hiding spots, which Bumann said is like looking for a needle in a haystack.

However, the researchers had a powerful experimental tool on their side, an imaging technology known as serial two-photon tomography. This technique enables scientists to obtain incredibly detailed, high-resolution images of tissues, layer by layer. The image slices are then consolidated to construct a three-dimensional view of the most intricate of tissues. In doing so, scientists can shine a spotlight on exactly where surviving bacteria are concealed.

The researchers used two-photon tomography to visualize the spleens of mice infected with Salmonella. The bacteria within the red pulp region of the spleen are typically eradicated with antibiotics. Interestingly, some bacteria were found to sneak into the spleen’s white pulp or lymphatic tissue.

“It’s ironic that pathogens hide in the body exactly where they should be caught as the culprit and an effective defense against them should be activated,” commented Bumann.

Armed with these new insights, Bumann and colleagues propose that boosting the immune system with immunotherapies may help stimulate neutrophils—immune cells that can help facilitate the clearance of bacteria to prevent possible relapses.