Scientists tested two new antimicrobial peptides modeled after the human protein LL‑37 and found they can stop Pseudomonas bacteria from sticking together and forming protective biofilms. The peptides work best when used early, but when a biofilm is already established, combining the peptides with regular antibiotics breaks it down much more completely than either alone.

<i>Pseudomonas aeruginosa</i> is involved in a variety of difficult-to-treat infections frequently due to biofilm formation. To identify useful antibiofilm strategies, this article evaluated efficacy of two newly engineered cationic antimicrobial peptides (17BIPHE2 and DASamP2), traditional antibiotics, and their combinations against biofilms at different stages. 17BIPHE2 is designed based on the 3D structure of human cathelicidin LL-37 and DASamP2 is derived from database screening. While both peptides show effects on bacterial adhesion, biofilm formation, and preformed biofilms, select antibiotics only inhibit biofilm formation, probably due to direct bacterial killing. In addition, the time dependence of biofilm formation and treatment in a static in vitro biofilm model was also studied. The initial bacterial inoculum determines the peptide concentration needed to inhibit biofilm growth. When the bacterial growth time is less than 8 h, the biomass in the wells can be dispersed by either antibiotics alone or peptides alone. However, nearly complete biofilm disruption can be achieved when both the peptide and antibiotics are applied. Our results emphasize the importance of antibiofilm peptides, early treatment using monotherapy, and the combination therapy for already formed biofilms of <i>P. aeruginosa</i>.