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

<b>Background:</b><i>Enterococcus faecalis</i> causes serious opportunistic infections in patients with weakened immune defenses, such as individuals suffering from malnutrition. We investigated the effects of <i>Lactiplantibacillus plantarum</i> MPL16 and CRL1506 on the resistance to <i>E. faecalis</i> infection in mice immunosuppressed by protein malnutrition. <b>Methods:</b> 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 <i>E. faecalis</i> 102. Infection levels in the gut, liver, spleen, and blood, intestinal tissue damage, and the cytokine response were evaluated 2 days after the challenge. <b>Results:</b> 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 <i>E. faecalis</i> and increases tissue damage, making the disease more severe than in animals renourished with BCD. Supplementing the BCD with <i>L. plantarum</i> strains significantly enhanced resistance to <i>E. faecalis</i> 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. <b>Conclusions:</b> Given their efficacy in enhancing host resistance, these <i>Lactiplantibacillus</i> strains hold great promise as a preventive strategy against <i>E. faecalis</i> infections in susceptible individuals.