Toward plant-based therapeutics: Unravelling the antibacterial, antibiofilm, and antiquorum-sensing actions of Acacia saligna extract

The universal spread of bacterial infections poses a significant issue in clinical settings. Pseudomonas aeruginosa is among the most commonly detected bacteria in various infections. Besides its resistance to multiple antibiotics, it also exhibits numerous virulence factors that hinder antibiotic treatment. Therefore, we intended to inspect the antibacterial and antivirulence consequences of Acacia saligna plant extract, along with phytochemical analysis of its active components by HPLC. The HPLC analysis identified 15 phenolic acids and flavonoid compounds. The A. saligna ethanol extract (ASE) demonstrated antibacterial activity, with minimum inhibitory concentrations (MICs) ranging from 128 to 1024 μg/mL. Additionally, ASE showed antibiofilm activity, reducing the percentage of vigorous and moderate biofilm-forming isolates from 78.57 % to 21.43 % as measured by the crystal violet assay. A significant downregulation of the QS genes in six out of eight P. aeruginosa isolates, with relative gene expression reduced to 0.1-0.4 for lasI, lasR, and rhlI genes, and 0.3-0.4 for rhlR gene compared to untreated controls. Furthermore, the in vivo antibacterial effects of ASE were demonstrated in P. aeruginosa-infected mice. There was a significant (p < 0.05) reduction in bacterial load in the kidneys, liver, and spleen of the ASE-treated group. Histopathological analysis revealed notable improvements in the kidney, liver, and spleen tissues in the ASE-treated group compared with the positive control. Immunohistochemical examination showed a lessening in the number of inflammatory marker-positive cells (TNF-α and IL-6). Additionally, there was a significant reduction (p < 0.05) in nitric oxide and malondialdehyde in the ASE-treated group. Therefore, ASE could be a promising antibacterial and antivirulence agent for treating P. aeruginosa infections.