How to kill the last microbes standing

Chemical wipes out bacteria that linger after antibiotic treatment

Using a chemical that prompts bacteria to self-destruct, scientists can exterminate germs that dodge an antibiotic. The new tactic, reported November 13 in Nature, could prevent chronic or recurrent infections.

Generally, an antibiotic knocks off around 99.99 percent of bacteria such as Staphylococcus aureus — as long as they’re not drug-resistant — and the body bumps off the rest. But for patients with weakened immune systems, the enduring microbes can cause persistent infections.

Kim Lewis of Northeastern University in Boston and colleagues found a molecule that induces lingering staph cells to destroy themselves. The compound binds to an enzyme that normally degrades broken proteins. Once bound, the enzyme becomes hyperactive and starts junking proteins indiscriminately.

When the researchers mixed the molecule with a standard antibiotic, they could kill 100 percent of staph cells in test tubes and in immune-compromised mice with chronic leg infections.

“It’s a very promising result,” says cell biologist Kenn Gerdes of Newcastle University in England, who was not involved with the study. Though the researchers tested the chemical only against staph,Gerdes says that virtually all bacteria include cells that persist after antibiotic treatment. The new method has potential to treat other types of infection, he adds.

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