In vitro antibacterial activity of Piper betel extract nanoemulsion and cannabidiol formulations against...

Canine pyoderma is a common dermatological condition, often caused by Staphylococcus pseudintermedius and related methicillin-resistant strains (MRSP and MRSS). Rising antimicrobial resistance necessitates alternative topical therapies. This study comparatively evaluated the in vitro antibacterial activity of P. betel leaf extract (both solvent-based and nanoemulsion forms) and cannabidiol (CBD) formulations against canine Staphylococcus isolates.

Antibacterial activity was determined by broth microdilution to establish minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Five formulations were tested: Ethanolic betel leaf extract in dimethyl sulfoxide betel leaf (BL), BL extract nanoemulsion (BLN), CBD in ethanol, water-soluble CBD, and CBD nanoemulsion. Test organisms included 15 Staphylococcus isolates (five MRSP, five methicillin-susceptible S. pseudintermedius, and five MRSS) and five Pseudomonas aeruginosa. Gas chromatography-mass spectrometry (GC-MS) was used to characterize phytochemical constituents.

GC-MS revealed eugenol (40.86%) and hydroxychavicol (26.44%) as predominant antibacterial compounds. BL and BLN demonstrated potent anti-staphylococcal activity, with median MICs of 0.16 g/L and 0.31 g/L, respectively. BL exhibited significantly lower MIC and MBC values than BLN (p = 0.008). Among CBD formulations, ethanol-dissolved and water-soluble CBD displayed the strongest activity (median MICs 0.003 g/L and 0.004 g/L), while CBD nanoemulsion was markedly less effective (median MIC 7.50 g/L). BLN also exhibited antibacterial activity against P. aeruginosa (median MIC 0.62 g/L), comparable to BL.

The novel BLN and soluble CBD formulations demonstrated significant in vitro antibacterial activity against methicillin-resistant Staphylococcus isolates from canine pyoderma. These results highlight their potential as topical antiseptic alternatives to chlorhexidine. Further in vivo studies are required to assess safety, efficacy, and formulation optimization. A combined betel-CBD nanoemulsion represents a promising direction for developing novel veterinary dermatological therapies.