In Vitro Antimicrobial Activity of Chlorhexidine–Curcumin Nanoformulations for Teat Dipping Against Mastitis Pathogens

Bovine mastitis is a major problem affecting dairy production, and teat disinfection is important for reducing the risk of bacterial infection. Curcumin has antimicrobial properties, but its poor water solubility limits its use in aqueous formulations. This study aimed to develop chlorhexidine–curcumin nanoformulations (CCNs) and perform preliminary in vitro screening of these nanoformulations as candidate teat-dipping formulations. Four CCNs containing increasing concentrations of curcumin (0%, 0.1%, 0.5%, and 0.9% w/v; CCN0, CCN0.1, CCN0.5, and CCN0.9, respectively) were prepared. CCN0, CCN0.1, and CCN0.5 were formulated as oil-in-water nanoemulsions, whereas CCN0.9 was prepared as a curcumin-β-cyclodextrin inclusion complex. The physicochemical properties were characterized, and the antibacterial activity was evaluated in vitro by agar well diffusion against six mastitis-associated pathogens. CCN0.9 showed the largest inhibition zones overall (20.07 ± 1.05–28.85 ± 1.05 mm; p < 0.05), while CCN0.1 and CCN0.5 showed activity comparable to or greater than that of commercial teat dips against several pathogens. CCN0.5 showed the most favorable nanoemulsion characteristics, with a particle size of 94.77 nm and a zeta potential of −46.57 mV. Overall, CCNs demonstrated antibacterial activity against mastitis pathogens, supporting their potential as candidate teat-dip formulations. Further teat irritation and in vivo efficacy studies are needed before field application.