Bactericidal activity of Piper betle L. extract against antibiotic resistant Salmonella spp. isolated from pig farms in Southern Thailand

Piper betle L. leaves have traditionally been used to treat various infectious diseases and to possess a wide spectrum of pharmacological effects. This study aimed to determine the antibacterial activity of the Piper betle leaf extract against antibiotic resistant Salmonella spp. isolated from pig farms located in Southern Thailand. Of this, 12 Salmonella spp. isolates were isolated from 24 pig fecal samples from 24 pig farms. The isolates were resistant to ampicillin (91.67%), penicillin (91.67%), tetracycline (81.81%), and doxycycline (81.81%). Antibacterial activity of the Piper betle ethanolic leaf extract against Salmonella spp. was carried out by disc diffusion assays, followed by Minimal inhibitory concentration (MIC) and Minimal bactericidal concentration (MBC) determination, as well as Time kill study. Piper betle extract exhibited antibacterial activity against all the isolates and S. Typhimurium with the inhibition zone ranged from 15.11 ± 0.34 to 20.30 ± 0.50 mm as observed by disc diffusion assay. The extract showed bactericidal activity against the isolates with the MIC and MBC values ranging from 0.5-1.0 mg/mL. Furthermore, the extract at 4 × MIC showed the killing activity with the reduction of the pathogen at least 3 logs within 8 h. The information suggests potential medicinal benefits of the Piper betle leaf extract to inhibit the growth of antibiotic resistant Salmonella spp. isolated from pig farms.