Safety Assessment of Eubacterium limosum El1405 and Its Protective Effect Against Salmonella Typhimurium Infection in Mice

Background/Objectives:Eubacterium limosum El1405 is a novel probiotic candidate strain that has been shown to exert prominent anti-inflammatory and anti-tumor bioactivities, with potential antibacterial activity against pathogenic bacteria. This study aimed to systematically evaluate the safety of E. limosum El1405 and its probiotic functions and protective effects against pathogenic bacterial infection. Methods: The safety of E. limosum El1405 was assessed through in vitro assays of hemolytic and gelatinase activities and a 28-day subchronic oral toxicity mouse model. In the mouse model, three different doses (low, medium, and high) of E. limosum El1405 were tested, and physiological status, visceral histopathology, hematological profiles, serum biochemistry, and cytokines were measured. The antibacterial activity of the strain against pathogenic bacteria was determined in vitro. A Salmonella Typhimurium -infected mouse model was used to assess its potential to protect against infection. Results: In vitro safety assays confirmed that E. limosum El1405 possessed no hemolytic or gelatinase activity. In the 28-day subchronic oral toxicity test, low, medium, and high doses of El1405 caused no significant alterations in mouse body weight, visceral index, organ histopathology, hematological parameters, serum biochemistry, or cytokine levels. The strain exhibited antibacterial activity against S. Typhimurium in vitro. In S. Typhimurium-infected mice, El1405 intervention effectively mitigated S. Typhimurium-induced damage, reduced visceral bacterial loads, decreased pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) in the ileum and serum, and elevated the anti-inflammatory cytokine IL-10. Conclusions:E. limosum El1405 displays a favorable safety profile and promising probiotic effects, including antibacterial capacity and anti-inflammatory protective effects against S. Typhimurium infection, supporting further exploration and development of E. limosum El1405 as a novel functional probiotic strain for clinical and health applications.