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

Abstract 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 while 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. IMPORTANCE Different from the action mechanism of traditional antibiotics, antibacterial strategies aimed at targeting bacterial virulence factors can effectively reduce bacterial pathogenicity without compromising bacterial growth and reproduction, making it a crucial research direction in combating bacterial drug resistance. Despite the influence of various factors on the expression of bacterial virulence factors, specific and consistently expressed virulence factors in certain bacteria can still serve as viable targets for drug development. In this study, we focused on outer membrane protein A, a key virulence factor of A. baumanni i, and successfully identified a highly specific antimicrobial peptide P92 through screening processes. Furthermore, our findings demonstrate its efficacy in various dynamic models for anti-infective therapy. These results validate that antibacterial agents targeting bacterial virulence factors possess relatively or absolutely narrow spectrum antimicrobial properties, enabling precise antibacterial action without inducing bacterial resistance.