lysozyme inhibitor LprI mediated by HmsP and c-di-GMP is essential for biofilm formation and virulence.

poses a significant threat, particularly to neonates and infants. Despite its strong pathogenicity, understanding of biofilms and their role in infections remains limited. This study investigates the roles of HmsP and c-di-GMP in biofilm formation and identifies key genetic and proteomic elements involved. Gene knockout experiments reveal that HmsP and c-di-GMP are linked to biofilm formation in . Comparative proteomic profiling identifies the lysozyme inhibitor protein LprI, which is downregulated in knockouts and upregulated in c-di-GMP knockouts, as a potential biofilm formation factor. Further investigation of the knockout strain shows significantly reduced biofilm formation and decreased virulence in a rat infection model. Additionally, LprI is demonstrated to bind extracellular DNA, suggesting a role in anchoring within the biofilm matrix. These findings enhance our understanding of the molecular mechanisms underlying biofilm formation and virulence in , offering potential targets for therapeutic intervention and food production settings.IMPORTANCE is a bacterium that poses a severe threat to neonates and infants. This research elucidates the role of the lysozyme inhibitor LprI, modulated by HmsP and c-di-GMP, and uncovers a key factor in biofilm formation and virulence. The findings offer crucial insights into the molecular interactions that enable to form resilient biofilms and persist in hostile environments, such as those found in food production facilities. These insights not only enhance our understanding of pathogenesis but also identify potential targets for novel therapeutic interventions to prevent or mitigate infections. This work is particularly relevant to public health and the food industry, where controlling contamination in powdered infant formula is vital for safeguarding vulnerable populations.