A phytochemical-nanotechnology platform exhibits complementary antimicrobial and immunomodulatory effects in...

Salmonella gallinarum, the causative agent of fowl typhoid, poses a persistent threat to poultry health and productivity, compounded by the growing problem of antibiotic resistance. Addressing the urgent need for effective alternatives, this study evaluated a multi-component complementary approach combining the phytocompound 4-hydroxycoumarin, silver nanoparticles (AgNPs), and Ajwain (Trachyspermum ammi) extract. In vitro assays, including antimicrobial susceptibility testing, cytotoxicity, and concentration optimization, confirmed the potent antibacterial activity and favorable safety profiles of the tested components. Molecular docking identified a putative interaction between 4-hydroxycoumarin and Chemokine (C-C motif) Ligand 5 (CCL5). Analysis of the archived molecular dynamics trajectory, after correction for periodic boundary conditions, revealed substantial protein conformational deviation and increasing ligand displacement toward the end of the trajectory, with a loss of close protein-ligand contact after approximately 40 ns. These findings support a predicted interaction but do not establish persistent ligand binding or a single predicted protein-ligand association mode. In the chicken infection model, the combination treatments were associated with descriptively reduced clinical severity and differences in endpoint mortality. These in vivo findings should be regarded as preliminary, descriptive, and exploratory proof-of-concept data, as mortality and clinical endpoint comparisons did not remain statistically significant after Holm correction. As 4-hydroxycoumarin was evaluated in vivo only as a component of the combination formulations, the observed effects belong strictly to the tested combinations, and their individual contributions cannot be determined independently. Gene expression analyses further revealed a downregulation of proinflammatory cytokines, providing exploratory evidence of immunomodulatory responses associated with the tested formulations. Together, these findings provide preliminary proof of concept for a multi-component approach against S. gallinarum infection.