Enhancing Resistance to Enterococcus faecalis: Immunobiotic Lactiplantibacillus plantarum Strains as a Strategy for Malnourished Hosts.

Background:Enterococcus faecalis causes serious opportunistic infections in patients with weakened immune defenses, such as individuals suffering from malnutrition. We investigated the effects of Lactiplantibacillus plantarum MPL16 and CRL1506 on the resistance to E. faecalis infection in mice immunosuppressed by protein malnutrition. Methods: Male BALB/c mice received a protein-deficient diet for 21 days, followed by a 7-day renourishment period with a balanced conventional diet (BCD) with or without lactobacilli supplementation. Malnourished controls (MN) and renourished mice were treated with gentamicin for 3 days and then challenged orally with E. faecalis 102. Infection levels in the gut, liver, spleen, and blood, intestinal tissue damage, and the cytokine response were evaluated 2 days after the challenge. Results: Malnourished mice had an impaired ability to produce pro-inflammatory cytokines (TNF, IFN-γ, IL-1β, IL-6, IL-17, and KC) and the regulatory IL-10 in response to the infection compared to mice in the BCD group. The imbalance of inflammatory and regulatory mediators in MN mice favors colonization and invasion by E. faecalis and increases tissue damage, making the disease more severe than in animals renourished with BCD. Supplementing the BCD with L. plantarum strains significantly enhanced resistance to E. faecalis 102 infections, as evidenced by a marked reduction in bacterial loads and intestinal damage. The effect of lactobacilli was associated with enhanced levels of IFN-γ, IL-6, and IL-10 and reduced TNF, IL-1β, IL-17, and KC. Conclusions: Given their efficacy in enhancing host resistance, these Lactiplantibacillus strains hold great promise as a preventive strategy against E. faecalis infections in susceptible individuals.