Preparation, in vitro and in vivo assessment of novel carvacrol@pro-phytomicelles for the treatment of Salmonella enteritidis infection in mice

In livestock and poultry farming, the use of antibiotics has been abused, which seriously endangers human health. Thus, antibiotic alternatives are urgently needed. The phytochemical carvacrol (CAR) has attracted attention as an antibiotic alternative due to its excellent antibacterial activity and anti-inflammatory activity. However, CAR has high volatility and low water solubility, which seriously affect its antibacterial activity. In this study, two plant-derived small-molecule phytochemicals-glycyrrhizin and rebaudioside A-were selected as nanocarriers for the preparation of a novel solid pro-phytomicelle formulation named as CAR@PP. Using a simple fabrication method, the encapsulation efficiency of CAR reached 98.74 ± 1.14 %. CAR@PP was found to rapidly dissolve in water, resulting in a transparent solution (named as CAR@M) and a 59-fold increase in solubility compared to CAR. CAR@M contained uniform nanoparticles with a particle size, polydispersity index, and zeta potential of 3.52 ± 0.93 nm, 0.17 ± 0.01, and -10.63 ± 0.45 mV, respectively. The in vitro antibacterial activity of CAR@M was evaluated, and the minimum inhibitory concentration for the tested strains was 125-250 μg/ml. The antibacterial mechanisms were found that CAR@M disrupted the bacterial wall and biomembranes and efficiently inhibited bacterial biofilm growth. To the in vivo activity evaluation, treatment with 50 mg/kg CAR@M could effectively improve bacterial liver abscesses, decrease the inflammatory cytokine levels in the liver and cecum, and reduce the bacterial load in the liver and feces in Salmonella enteritidis-infected mice. In conclusion, CAR@PP is a promising alternative to antibiotics in livestock and poultry farming warranting further research.