How dangerous foodborne bacteria resist common disinfectants
Oeiras, 11th March 2025
Listeria monocytogenes causes listeriosis, one of the most severe foodborne diseases. Although the number of cases is small, estimated at around five per million people annually in Europe, this disease is associated with high hospitalization rates. Moreover, listeriosis ranks as the third leading cause of death from foodborne illness highlighting its significant public health impact.
Listeria infections occur mainly due to the consumption of contaminated food from both animal and plant sources. But controlling L. monocytogenes proliferation is challenging due to its ability to spread through the food chain, and grow even in cold storages. In a new study published in the international Journal “Free Radical Biology and Medicine”, ITQB NOVA researchers uncovered a mechanism that helps these pathogens withstand hydrogen peroxide, a common antimicrobial agent.
The key player in this process is Hfq, a protein that binds to the bacterial messenger RNA (mRNA). Cecília Arraiano, head of the Control of Gene Expression Lab at ITQB NOVA, explains: “If DNA is like an architect who provides a plan for a house, RNA is the molecule that deciphers the design and brings what is necessary for the construction of the building”. In bacteria, some messenger RNAs bring the instruction how to produce “catalase”, an enzyme that breaks down hydrogen peroxide into water and oxygen. “Hfq stabilizes mRNA, making it less labile ensuring that bacteria keep producing the levels of catalase needed to fight the harmful hydrogen peroxide”, explains André Seixas, PhD student at ITQB NOVA and first author of the paper.
This research has important implications not only for food safety, but also for public health. In fact, after surviving hydrogen peroxide in the food chain, these bacteria face the same molecule again inside the human body, this time as a weapon of the immune system. This led the research team to ask: “what if we could turn Hfq off?”. The answer is promising: “in the absence of this protein, the bacteria become highly vulnerable to hydrogen peroxide, both in lab tests and inside immune cells”, explains José Marques Andrade, leader of the study.
These findings reveal a new factor in L. monocytogenes' stress response, improving our understanding of bacterial defenses. This could lead to new infection control strategies targeting Hfq, making the bacteria more vulnerable to immune cells, disinfectants, and antibiotics.
ITQB NOVA researchers (from the left to the right) Alda Silva, João Sousa (back row), Cecília Arraiano, André Seixas and José Andrade (front row)
