Natural medicine can substitute antibiotics in animal husbandry: Protective effects and mechanisms of rosewood essential oil against Salmonella infection

Aniba rosaeodora essential oil (RO) is widely used in traditional natural medicine replacing antibiotics due to its antidepressant and antibacterial properties. Salmonella is commonly found in foodborne diseases and is a major threat to the efficacy of antibiotics. However, the potential antibacterial efficiency and mechanisms of RO against Salmonella spp. have not been extensively explored. Our work aims to analyse the chemical composition of RO, and reveal the activity and mechanism of RO against Salmonella in vitro, and further delineate the underlying anti-inflammatory mechanisms of action when Salmonella infection occurs in vivo. Gas chromatography‒mass spectrometry (GC‒MS) was utilized to identify the ingredients of RO. Minimal inhibitory concentration (MIC) and time-kill assays were used to examine the antibacterial activity of RO. A series of biochemical assays were applied to determine the potential bactericidal mechanism. Both mouse and chick models of Salmonella infection were established to evaluate the preventive effects of RO treatment. RO showed antibacterial activity against both gram-positive bacteria and gram-negative bacteria. The MIC of RO for Salmonella spp. was 4 mg/mL. RO-treated Salmonella was damaged owing to the disruption of lipid and purine metabolism. Additionally, RO alleviated injury and decreased microbial colonization in infected mice and chicks. Furthermore, RO treatment inhibited the host inflammatory response by reducing the proinflammatory pathway. In summary, our results provide evidence that natural RO is effective for Salmonella infection, which paves the way for developing this essential oil as an antibiotic substitution for antibacterial infection.