Antibiofilm activity of berberine against Staphylococcus aureus

Berberine, a naturally occurring isoquinoline alkaloid, has demonstrated strong antibiofilm properties against Staphylococcus aureus. However, the molecular mechanisms underlying this activity remain poorly understood. Here, we report that berberine effectively inhibits S. aureus biofilm formation with a minimum biofilm inhibitory concentration (MBIC) of 32 µg ml^-1. XTT assays demonstrated a marked reduction in biofilm metabolic activity, while high-content screening (HCS) combined with three-dimensional reconstruction revealed significant decreases in biofilm biomass and thickness. Mechanistically, berberine selectively suppressed the production of key extracellular polymeric substance (EPS) components, particularly polysaccharide intercellular adhesin (PIA) and proteins, without significantly affecting extracellular DNA (eDNA) levels. Transcriptomic profiling integrated with protein-protein interaction (PPI) network modeling suggested that srrA, a response regulator within the two-component system, may serve as a central hub gene downregulated by berberine. Quantitative PCR (qPCR) further corroborated the altered expression of srrA and associated genes (walR, atpB, luxS, icaR). Collectively, these findings provide mechanistic insights into berberine's antibiofilm activity and point to srrA-mediated EPS regulation as a candidate pathway warranting further investigation.