The mucus lining our intestines is decorated with sugars, which are an important food source for bacteria living in the gut. However, friendly gut microbes aren’t the only ones who devour mucus-derived sweets. The diarrhea-inducing bacterium, Clostridioides difficile (C.diff), also consumes sugars to survive in the gut. 

Normally, resident gut bacteria resist C. diff infection (CDI) by hogging nutrients this nasty bug needs to live. Antibiotic treatment is a major risk factor for CDI, as it depletes the populations of these resident gut bacteria. While it is known that restoring beneficial members of the gut bacterial community can help fight CDI, the use of microbes that specifically inhibit C. diff mucus consumption is an area of untapped therapeutic potential. 

However, a recent study published in Nature Communications suggests such therapies might be worth pursuing.

Researchers incubated mouse poop with various mucosal sugars suspended in “heavy water”, a form of H₂O in which hydrogen is replaced by its heftier sibling, deuterium. This allowed researchers to track which bacteria were eating the sugars in the mouse poop by looking at which contained deuterium and which did not. Five bacteria that specifically consumed C. diff-preferred mucosal sugars were combined to create a consortium of bacteria that could prevent C. diff from accessing its food. The researchers called this group, "BacMix." 

They found that when C. diff was incubated with its preferred food sugars in the presence of BacMix, it grew worse than if incubated alone. The researchers treated mice with BacMax and then infected them with C. diff, and saw a similar trend. The mice exhibited a gradual decrease in C. diff intestinal levels over time, indicating that this bacterial “cocktail” capable of resisting C.diff colonization. 

These findings suggest that barring C. diff from the proverbial candy store may help prevent or treat CDI. More broadly, this study forms a basis for identifying gut bacteria with specific functions (e.g. sugar-eating) to inform the design of effective microbe-based therapeutics.