Carboxymethyl chitosan prevents formation of broad-spectrum biofilm

In this study, we determined the effect of carboxymethyl chitosan (CM-chitosan) on biofilm formation and proposed a mechanism. Gram-positive and Gram-negative bacterial biofilm formation on microtiter plates was prevented 74.6% and 81.6% by CM-chitosan, respectively. Biofilm formation was also severely prevented in dynamic conditions. CM-chitosan inhibits the adhesion of bacteria with an efficiency of >90%. It prevents Gram-positive bacterial biofilm formation at efficiencies of 63.1% and Gram-negative bacterial biofilm formation at efficiencies of 70.6% when CM-chitosan is added at 1 h after biofilm initiation. The prevention of initial bacterial adherence and cell–cell interaction was ascribed to flocculation. The flocculation of Gram-positive and Gram-negative bacteria was 16.7% and 24.6% in the presence of CM-chitosan, respectively. CM-chitosan may neutralize bacterial surface charge and bridge the bacterial aggregates. CM-chitosan decreased 12.9% and 12.8% of the cell surface charge of Staphylococcus aureus and Pseudomonas aeruginosa, respectively. CM-chitosan may serve as an antibiofilm agent.