Enhancing food system protection: synergistic action of engineered endolysin LYSMP and berberine hydrochloride against Streptococcus suis on pork

This study presents a synergistic bactericidal strategy combining engineered phage endolysin LYSMP-HPP with the plant-derived agent berberine hydrochloride (Bh) for controlling Streptococcus suis in foods and clinical settings. LYSMP-HPP, modified with a C-terminal hydrophobic short peptide (HPP), exhibits enhanced stability under food processing conditions (pH 5-7, heat, metal ions) while maintaining broad-spectrum bacteriolytic activity. In combination, LYSMP-HPP and Bh showed a strong synergistic effect on S. suis, reducing the minimum inhibitory concentration (MIC) of Bh to 1/8 compared to its use alone. LYSMP-HPP was shown to target specifically the hydrolysis of the cell wall peptidoglycan, while Bh disrupts membrane integrity, inhibits virulence genes expression and damages bacterial DNA, collectively leading to cellular collapse. Moreover, the combined treatment significantly downregulated genes encoding virulence factors and biofilm exopolysaccharides, as well as enhanced biofilm clearance and formation on porcine skin. In addition, bacterial load on pork surface was reduced by 4-5 Log₁₀ CFU/g without affecting sensory quality. Safety assessments showed a 5 % decrease in the hemolysis rate and an 85 % increase in cell viability. In vivo experiments further revealed reduced bacterial load and damage in tissues. The strategy proposed herein is an efficient and safe solution for bio-preservation and a multi-target therapeutic option against resistant infections. Future work will focus on optimizing its scalability for industrial application.