Co-encapsulation of formic acid and Satureja hortensis essential oil enhances antibacterial and anti-inflammatory activities against Salmonella enterica.

The emergence of multidrug-resistant Salmonella enterica has increased the need for alternative antibacterial strategies based on natural bioactive compounds with multifunctional properties. This study developed spray-dried co-encapsulated formic acid (FA) and Satureja hortensis essential oil (SEO) nanocapsules and evaluated their physicochemical properties, antibacterial activity, and anti-inflammatory potential. GC-MS analysis showed SEO was rich in carvacrol (41.26%), thymol (18.74%), p-cymene (14.32%), and γ-terpinene (11.48%). SEM and DLS analyses indicated spherical nanoparticles with a mean dry diameter of 442.91 nm and a hydrodynamic diameter of 346.93 nm (PDI 0.246), indicating uniform distribution. Encapsulation efficiency was 81.47 ± 2.16%. The formulation showed strong antibacterial activity against Salmonella enterica, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Klebsiella pneumoniae in disk diffusion, MIC, and MBC assays. In vivo, Salmonella-infected BALB/c mice receiving FA-SEO nanocapsules showed improved body weight, feed intake, antioxidant enzymes, and immunoglobulin levels, with reduced liver enzymes and intestinal inflammation. Histopathology confirmed protective effects on intestinal and hepatic tissues, while iNOS expression in the jejunum was significantly reduced, indicating anti-inflammatory action. Overall, FA-SEO co-encapsulation enhanced stability and biological activity, offering a promising supportive strategy against Salmonella infection and inflammation, though further mechanistic and safety studies are needed. These findings suggest that combining organic acid and essential oil components through nano-encapsulation may improve antimicrobial stability, enhance bioavailability, and enable synergistic interactions between active compounds, thereby increasing efficacy compared with non-encapsulated forms. Such multifunctional nanoformulations may also reduce required dosages, minimize potential side effects, and provide a natural alternative to conventional antibiotics in food-producing animals, contributing to antimicrobial resistance mitigation strategies. Moreover, the observed modulation of inflammatory markers such as iNOS highlights the potential immunomodulatory role of the formulation beyond direct antibacterial effects, supporting tissue protection during infection. Further long-term in vivo studies are required to confirm safety, dosage optimization, and mechanistic pathways and clinical applicability in the future.