The natural peptide LL‑37 can break down the protective slime layer (biofilm) that Acinetobacter baumannii bacteria form, even at doses much lower than needed to stop the bacteria from growing. In lab tests, a tiny amount (2.5 µg/ml) already caused visible damage, and higher amounts kept reducing the biofilm.

To investigate the effect of antibacterial peptide LL-37 on the integrity of Acinetobacter baumannii biofilm. A model of Acinetobacter baumannii biofilm in vitro was constructed by plates and crystal violet staining method, and the minimal inhibitory concentration of LL-37 was determined by broth dilution. The biofilm morphology was observed by scanning electron microscopy and biofilm formation was analyzed by the crystal violet staining of the adherent biofilm in the presence of antibacterial peptide LL-37. In the Acinetobacter baumannii biofilm model, the minimal inhibitory concentration of LL-37 was 64 µg/ml; LL-37 caused structural damage of the biofilm at a low concentration of 2.5 µg/ml. The biofilm was decreased gradually as the concentration of LL-37 increased. LL-37 even at a concentration far below its minimal inhibitory concentration can cause structural damage of Acinetobacter baumannii biofilm in vitro.