Why is Listeria So Tough to Treat? Experts See Through its Stealth

The dangerous and highly adaptable food borne illness Listeria monocytogenes is reportedly extremely difficult to treat when treatment is necessary. Now researchers think they have figured out why this is, potentially opening up doors for strategies and treatment options.

According to the US Centers for Disease Control and Prevention (CDC), Listeriosis affects 1,600 Americans, killing about 260 every year. For most, the bacterial infection passes in a few days, causing fever, muscle ache and intestinal problems. However, for those particularly vulnerable - namely pregnant women and the elderly - a persistent infection can prove fatal. In these cases, treatment is required.

"Generally speaking, Listeria must be described as extremely adaptable," researcher Birgitte Kallipolitis explained in a recent release. "It is constantly aware of its surroundings and if the environment changes around it, it reacts instantly and has a number of strategies to withstand threats."

Alongside several of her colleagues Kallipolitis recently put the Listeria bacterium through what could be described as the standard resistance gauntlet, exposing it to antibiotics, bile, salt, acid and ethanol - all harmful environments that it would traditionally encounter.

The results were recently published in the journal Nucleic Acids Research.

"We knew that Listeria can resist these substances, but we did not quite know how," Kallipolitis said.

What they found was that the bacterium started producing special RNA molecules when exposed to specific adverse conditions.

"With these RNA molecules the bacteria can adjust how much or how little to produce of various proteins. For example it can downgrade the production of the protein LapB, which it uses to enter our cells. If this production is not downgraded, the bacterium will potentially be detected and fought by the immune system," Kallipolitis explained.

But by downplaying its presence, the Listeria can stick around longer, waiting for a more ample opportunity to strike.

According to the authors, understanding this stealthy strategy can undoubtedly help professionals better determine how to tackle a persistent infection, potentially saving hundreds of lives each year.