Researchers in Australia have made a discovery that could help to add options when treating Listeria infections.

Scientists at the University of Queensland have found a way to block Listeria from making the virulence proteins that allow bacteria to survive and multiply in immune cells.

The hope is the findings, published in the journal PLOS Pathogens, could help the development of new drugs to treat Listeria monocytogenes infections.

Professor Antje Blumenthal said once ingested, Listeria can hide from the body’s immune system and multiply inside cells.

“Instead of killing the bacteria, the immune cells are used by the bacteria to multiply and are often killed by Listeria growing inside them. Our study showed the bacteria could be cleared with a small drug-like inhibitor that targets the master regulator of the proteins that help Listeria grow in immune cells. The inhibitor helped the immune cells survive infection and kill the bacteria,” she said.

Stopping Listeria growth in immune cells
Listeria’s virulence genes are controlled by positive regulatory factor A (PrfA). Findings encourage further exploration of PrfA as a potential target for antimicrobials. Scientists tracked what happened to Listeria when PrfA is inhibited over several days using different studies.

Previous studies into the master regulator — which controls proteins that make Listeria virulent ­­– have mostly been based on engineered bacteria, or mutated versions of these proteins.

Blumenthal said the discovery and other work could guide the development of inhibitors and drugs to treat listeriosis.

“By using a drug-like inhibitor, we were able to use molecular imaging and infections studies to better understand what happens to Listeria when the bacteria cannot effectively grow inside immune cells and hide from immune defense mechanisms. This could add new options for treating Listeria infections and improve health outcomes for patients with complications arising from listeriosis,” she said.

The study also included researchers from Umeå University, Sweden; the Australian Infectious Diseases Research Centre; Institute for Molecular Bioscience; Mater Research Institute; Telethon Kids Institute, University of Western Australia; Monash University; University of Melbourne and Hudson Institute of Medical Research.

About Listeria infections
Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still cause serious and sometimes life-threatening infections. Anyone who has developed symptoms of Listeria infection should seek medical treatment and tell their doctors about possible Listeria exposure.

Also, it can take up to 70 days after exposure to Listeria for symptoms of listeriosis to develop.

Symptoms of Listeria infection can include vomiting, nausea, persistent fever, muscle aches, severe headache, and neck stiffness. Specific laboratory tests are required to diagnose Listeria infections, which can mimic other illnesses.

Pregnant women, the elderly, young children, and people such as cancer patients who have weakened immune systems are particularly at risk of serious illnesses, life-threatening infections, and other complications. Although infected pregnant women may experience only mild, flu-like symptoms, their infections can lead to premature delivery, infection of the newborn, or even stillbirth.

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