A peptide targeting outer membrane protein A of Acinetobacter baumannii exhibits antibacterial activity by reducing bacterial pathogenicity.

The World Health Organization has classified multidrug-resistant (MDR) Acinetobacter baumannii as a significant threat to human health, necessitating the urgent discovery of new antibacterial drugs to combat bacterial resistance. Outer membrane protein A of A. baumannii (AbOmpA) is an outer membrane-anchored β-barrel-shaped pore protein that plays a critical role in bacterial adhesion, invasion, and biofilm formation. Therefore, AbOmpA is considered a key virulence factor of A. baumannii. Herein, we screened three phage display peptide libraries targeting AbOmpA and identified several peptides. Among them, P92 (amino acid sequence: QMGFMTSPKHSV) exhibited the highest binding affinity with AbOmpA, with a KD value of 7.84 nM. In vitro studies demonstrated that although P92 did not directly inhibit bacterial growth, it significantly reduced the invasion and adhesion capabilities of multiple clinical isolates of MDR A. baumannii and concentration-dependently inhibited biofilm formation by acting on OmpA. Furthermore, the polymerase chain reaction results confirmed a significant positive correlation between the antibacterial effect of P92 and OmpA expression levels. Encouragingly, P92 also displayed remarkable therapeutic efficacy against A. baumannii infection in various models, including an in vitro cell infection model, a mouse skin infection model, and a mouse sepsis model. These results highlight P92 as a novel and highly effective antimicrobial molecule specifically targeting the virulence factor AbOmpA.