A Bacteriophage Cocktail Significantly Reduces Listeria monocytogenes without Deleterious Impact on the Commensal Gut Microbiota under Simulated Gastrointestinal Conditions Original paper

What was studied?

This study examined the effectiveness of a bacteriophage cocktail (FOP) on reducing Listeria monocytogenes levels in the gastrointestinal tract, specifically under simulated conditions that mimic human digestion. The researchers tested the ability of the FOP cocktail to survive gastric passage, reduce Listeria counts in the small and large intestines, and preserve the commensal gut microbiota. The study also assessed the ability of the phage cocktail to protect human intestinal cells (Caco-2) from adhesion and invasion by Listeria.

Who was studied?

The study focused on the bacterium Listeria monocytogenes, a foodborne pathogen responsible for severe infections like listeriosis. The study used both in vitro models, including a simulated small intestine model (TSI), colon model (CoMiniGut), and Caco-2 cells, to evaluate the efficacy of the FOP bacteriophage cocktail. It also involved the study of the commensal microbiota using 16S rRNA sequencing to monitor any changes in the bacterial community composition after phage treatment.

What were the most important findings?

The study found that the FOP bacteriophage cocktail significantly reduced Listeria monocytogenes levels in both the small intestine and colon under simulated gastrointestinal conditions. Phage treatment resulted in a substantial reduction in Listeria in the ileum (1.5-log reduction) and in the colon (3-5-log reduction), without significantly affecting the other commensal bacteria in the gut. This finding suggests that the phages selectively target Listeria, preserving the balance of the gut microbiota. In contrast, ampicillin treatment also reduced Listeria levels but led to a significant loss of commensal gut bacteria. Additionally, the FOP cocktail was more effective than ampicillin in preventing Listeria from adhering to and invading Caco-2 intestinal epithelial cells, showing a 5-log reduction compared to a 1-log reduction with ampicillin. The phage cocktail also did not induce an inflammatory response or alter transepithelial resistance (TER) in the Caco-2 cells, suggesting that it did not negatively affect the integrity of the intestinal barrier.

What are the greatest implications of this study?

The findings of this study suggest that bacteriophage therapy could be a highly effective and selective approach to reduce Listeria monocytogenes contamination in the gastrointestinal tract without harming the beneficial gut microbiota. This is particularly important for maintaining gut health, especially in individuals with sensitive microbiomes, such as those undergoing immunosuppressive treatments or suffering from conditions like irritable bowel syndrome. The study provides strong evidence that the FOP bacteriophage cocktail could be developed into a therapeutic or preventive intervention against Listeria infections, potentially offering a complementary or alternative strategy to traditional antibiotics, especially in light of rising antibiotic resistance.