Thymol@pro-phytomicelles as an antibiotic alternative in livestock and poultry farming: preparation, characterization, and in vitro and in vivo antimicrobial activity evaluation

Antibiotic abuse in livestock and poultry farming poses significant threats to human health, including the emergence of drug-resistant bacteria. Thus, antibiotic alternatives are highly required in this field. Thymol (THY) demonstrates significant potential as an antibiotic alternative, but its commercial application is limited due to its high volatility and low water solubility. In this study, a novel nanoformulation of pro-phytomicelles, with glycyrrhizin and rebaudioside A as mixed-nanocarriers that load THY (called “THY@pro-phytomicelles”), was designed and tested as a potent antibiotic alternative. The optimized THY@pro-phytomicelles had an encapsulation efficiency of 99.75 ± 0.37 % and a particle size of 3.83 ± 0.44 nm after they were dispersed in water. Following THY’s formulation into THY@pro-phytomicelles, its water solubility, volatility stability, and antioxidant activity significantly improved. In vitro, the THY@pro-phytomicelles showed better antimicrobial activity than THY. Their antibacterial mechanism appeared to involve destruction of the integrity of the bacterial cell wall and biomembrane, leading to alkaline phosphatase (AKP) leakage and inhibition of biofilm formation. In the animal evaluation in this study, they showed excellent in vivo antibacterial capacities against Salmonella enteritidis-induced enteritis, including improvement of the liver bacterial abscess, alleviation of the oxidative stress and inflammatory cytokine levels, reduction of the bacterial load of the liver, and alleviation of the inflammation and damage caused by bacteria in the cecum. Overall, the THY@pro-phytomicelles showed excellent in vitro and in vivo antibacterial activity, making them a potentially effective antibiotic alternative in livestock and poultry farming, with broad potential application in the breeding industry.