Synergistic Effect of Eugenol and Probiotic Lactobacillus Plantarum Zs2058 against Salmonella Infection in C57bl/6 Mice

Previously, we showed the preventive effects of Lactobacillus plantarum ZS2058 (ZS2058) on Salmonella infection in murine models. In this work, we found that eugenol has a selective antibacterial effect, which inhibited Salmonella more than probiotics ZS2058 in vitro. It suggested a synergistic effect of them beyond their individual anti-Salmonella activity. We verified the conjecture in murine models. The results showed that the combination of ZS2058 and eugenol (CLPZE) significantly increased (p = 0.026) the survival rate of Salmonella-infected mice from 60% to 80% and the effect of CLPZE on preventing Salmonella-infection was 2-fold that of ZS2058 alone and 6-fold that of eugenol alone. CLPZE had a synergistic effect on inhibiting ST growth (the coefficient drug interaction ((CDI) = 0.829), reducing its invasiveness (CDI = 0.373) and downregulating virulence genes’ expression in vitro. CLPZE helped the host form a healthier gut ecosystem. CLPZE also elicited a stronger and earlier immune response to systemic infection. In conclusion, these obtained results suggest that ZS2058 and eugenol have a synergistic effect on preventing Salmonella infection and open new perspectives in the strategies of controlling the prevalence of Salmonella by combination of probiotics and functional food components.