Biogenic silver nanoparticles synthesized with Eucalyptus camaldulensis aqueous leaf extract, a novel anti-virulence strategy for attenuating Acinetobacter baumannii outer membrane protein A

Outer membrane protein A (OmpA) is a major virulence factor responsible for Acinetobacter baumannii pathogenesis, immunogenicity, and induction of inflammatory response. In this study, biogenic silver nanoparticles (AgNPs) were synthesized and employed as bioactive agents for attenuation of A. baumannii OmpA. Synthesized AgNPs were characterized using ultraviolet-visible spectra, X-ray diffractogram, fourier transform infrared spectroscopy, and transmission electron microscope. Surface plasmon resonance peak was observed at 411 nm, and average calculated crystallite size of AgNPs ranged between 12.57 to 84.69 nm. In addition, AgNPs morphology showed spherical and oval shaped. The nanoparticles displayed antibacterial effects with minimum inhibitory concentration values ranging from 2.70 to 5.40 µg/mL. Silver nanoparticles significantly attenuated the expression of OmpA up to 70% (p < 0.001). At concentration 5.40 µg/mL, AgNPs reduced OmpA mediated nitric oxide production by 15.68 µM compared with positive control (p < 0.001). Additionally, AgNPs treatment significantly decreased bacterial DNA content (p < 0.05). This work suggested that green synthesized AgNPs could be a potential therapeutic anti-virulence agent for the attenuation of A. baumannii OmpA.