What's the News: Adding sugar to certain antibiotics can boost their bacteria-battling ability, according to a study
published today in Nature. In particular, sugar helps the drugs wipe out persisters, bacteria that evade antibiotics
by essentially going dormant only to flare up again once the danger has passed. This technique could lead to the development of inexpensive, more effective treatments for bacterial infections. How the Heck:
The study looked at two common bacteria: E. coli, which can lead to urinary tract and gastrointestinal infections, and Staphylococcus aureus, the bugs that cause staph infections. Both can be treated with gentamicin, one of a larger group of antibiotics called aminoglycosides.
The researchers combined gentamicin with different kinds of sugars, including mannitol, fructose and glucose. (Sucrose, the stuff you put in your coffee, is just one of many types of sugars as far as biochemistry's concerned.
When the scientists added these sweetened antibiotics to bacteria grown in Petri dishes, it killed over 99% of the bacterial persisters. The type of sugar seemed to make a difference, as well; only fructose helped the drug kill S. aureus, for instance.
The goal, said senior author James Collins, was essentially to "get them up off the ground so we can punch them and knock them out," and it seems to have worked. The sugar got the bacterial persisters to wake up out of their dormant state just enough that they took in the antibiotics, which killed them.
The researchers also used sugar-gentamicin combinations to kill these bacteria under two sets of circumstances somewhat closer to the clinic: in biofilms, layers of bacterial goo that often form on medical devices and are particularly hard to wipe out, and in mice with urinary tract infections.
What's the Context:
Bacterial persisters are often responsible for recurrent bouts of diseases like strep throat, staph, and urinary tract infections, but no current treatments directly target them.
Treating persistent infections with existing antibiotics and sugar would allow doctors to use existing drugs, rather than wait for new ones to come along. By making existing treatments more effective, this technique could also save patients the expense and unpleasantness of taking multiple courses of antibiotics.
Not So Fast:
As with any treatment that's only been tested in cells and mice, there are wrinkles that must be ironed out before the drug is used in people. One such worry is that human patients will simply digest the sugar before it gets to where the bacteria are---though mannitol, one of the sugars used, isn't digestible by people.
Sugar seems to give a bacteria-killing boost only to aminoglycines, not to all antibiotics.
The Future Holds:
The researchers are now investigating whether the same technique will strengthen antibiotics that fight tuberculosis.
Reference: Kyle R. Allison, Mark P. Brynildsen, & James J. Collins. "Metabolite-enabled eradication of bacterial persisters by aminoglycosides." Nature, May 12, 2011. DOI:10.1038/nature10069
Image: US Department of Agriculture