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Boosting vaccines with harmless bacteria to fight intestinal pathogens

Published in Science, a ground-breaking study by the Slack group reveals how combining vaccines with friendly bacteria can boost vaccination efficacy and potentially reduce reliance on antibiotics.

The international collaboration between Professor Emma Slack, from the Dunn School and the ETH Zurich, and Professor Médéric Diard  from the Biozentrum at the University of Basel, has developed a game-changing approach to combat harmful intestinal bacteria. Their research, conducted in mice, shows that combining oral vaccines with harmless bacteria is a highly effective approach to improving vaccine efficacy. The harmless bacteria outcompete the pathogenic bacteria for nutrients in the intestine, working in synergy with the vaccine to eliminate pathogenic bacteria more effectively than vaccination or treatment with harmless bacteria alone.

This combined approach not only prevented Salmonella infection in mice, but also eliminated established pathogenic E.coli infections. For this approach to work, the harmless bacteria must be able to thrive in the same environment as the pathogenic bacteria, with similar nutrient, oxygen and acidity requirements. The researchers used genetic engineering to develop a competitive harmless bacteria strain, though naturally selected E. coli strains were also effective.

“Although we can decimate pathogenic bacteria with a vaccine, we need harmless microorganisms to fill the resulting niche in the intestinal ecosystem in order to achieve long-term success,” explained Professor Slack. “It’s like gardening. If you want to avoid weeds in an area of the garden, you must plant other plants there after weeding. If you leave the soil empty, the weeds will just grow back.”

In the fight against antimicrobial resistance, this method offers a promising alternative to antibiotics, targeting pathogens without contributing to resistance. It opens the door for future research aimed at applying this approach in humans, offering the potential to eliminate antibiotic-resistant strains and improve public health.

Research article: Lentsch V, Woller A, Rocker A, Aslan S, Moresi C, Ruoho N, Larsson L, Fattinger SA, Wenner N, Cappio Barazzone E, Hardt WD, Loverdo C, Diard M, Slack E: Vaccine-enhanced competition permits rational bacterial strain replacement in the gut, Science 2025

Written by Isabella Maudlin (Hinch lab)

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