Why Listerium Bacterium is So Hard to Fight: Immune System Avoidance

Listeria can be an extremely difficult bacterium to fight. In fact, over the last few weeks it's infected 28 people from Denmark and has caused 13 to die. Now, though, scientists have taken a closer look at what makes this bacterium so resilient to treatments.

In order to learn a bit more about Listeria, the researchers tested how it reacted when it was exposed to a number of substances, such as antibiotics, bile, salt, acid and ethanol. In addition, they exposed it to conditions similar to what it encounters in food, in the human body and during disinfection.

"We knew that Listeria can resist these substances, but we did not quite know how," said Birgitte Kallipolitis, one of the researchers, in a news release. "Generally speaking, Listeria must be described as extremely adaptable. 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."

That's not all that the researchers found, though. The scientists also discovered that the bacterium is an expert at avoiding the body's immune system.

"One the one hand, Listeria needs to produce some special proteins that enable it to infect the cells in our body," said Kallipolitis. "On the other hand, it must ensure that the body's immune system does not detect these proteins. It is vital for Listeria to keep a balance between producing enough of these proteins but not so many that they are detected by the immune system-and it masters just that."

Listeria can also fine-tune the production of proteins needed to infect our cells to the point where it can sneak through the immune system's defense. This, in particular, reveals why this particular bacterium can be so dangerous to human health.

"Only by looking at what the bacteria themselves do to survive can we become better at fighting their pathogenicity," said Kellipolitis.

The findings are published in the journal Nucleic Acids Research.