Modified probiotics, the beneficial bacteria touted for
their role in digestive health, could one day decrease the risk of Listeria
infection in people with susceptible immune systems, according to Purdue University
Arun Bhunia, a professor of food science; Mary Anne
Amalaradjou, a Purdue postdoctoral researcher; and Ok Kyung Koo, a former
Purdue doctoral student, found that the same Listeria protein that allows the
bacteria to pass through intestinal cells and into bloodstreams can help block
those same paths when added to a probiotic.
“Based on the research, it looks very promising that
we would get a significant reduction in Listeria infections,” said Bhunia,
whose findings were published in PLoS One.
Bhunia’s earlier work showed that Listeria triggers intestinal cells to express heat shock protein 60
on their surfaces. That allows Listeria
to bind to the intestinal cells using an adhesion protein and pass into them,
acting as a sort of gateway to the bloodstream.
Once in the bloodstream, even small doses of Listeria can cause fever, muscle aches,
nausea and diarrhea, as well as headaches, stiff neck, confusion, loss of
balance, and convulsions if it spreads to the nervous system. It can also cause
abortion and stillbirth in pregnant women.
According to the U.S. Centers for Disease Control and
Prevention, it sickens about 1,500 and kills 255 people each year in the United States
and primarily affects pregnant women, newborns, older adults, and those with
weakened immune systems.
“We’re seeing fewer Listeria infections, but the
severity of those infections is still high,” Amalaradjou said.
The researchers found that probiotics alone were
ineffective in combatting Listeria, so they stole a trick from the bacteria’s
own playbook. By adding the Listeria
adhesion protein to the probiotic Lactobacillus
paracasei, they were able to decrease the number of Listeria cells that passed through intestinal cells by 46%, a
significant decrease in the amount of the bacteria that could infect a
With the adhesion protein, Lactobacillus paracasei interacts with heat shock protein on the
surface of intestinal cells just as Listeria
would. The probiotic then attached to the intestinal cells, crowding out Listeria.
“It’s creating a competition,” Bhunia said.
“If Listeria comes in, it
doesn’t find a place to attach or invade.”
Bhunia said he could one day foresee the development of a
pill or probiotic drink that could be given to at-risk patients to minimize the
risk of Listeria infection.
The results came from tests on human intestinal cells. The
next step would be animal testing. Bhunia said that would allow him to see
whether different doses would have a greater effect.
Filed Under: Drug Discovery