Antimicrobial Effects of Medicinal Plant Species on Salmonella typhimurium Strains Isolated from Poultry Feces Samples

Abstract

Background: It has been proven that plant extracts show great promise in fighting pathogenic microorganisms. This study aimed to evaluate the resistance of 20 strains of Salmonella typhimurium extracted from poultry feces against conventional antibiotics and the antibacterial activity of 10 medicinal plant extracts, including Hibiscus sabdariffa L., Capparis spinosa L., Azadirachta indica A. Juss., Eryngium planum L., Rumex acetosa L., Calotropis procera (Aiton) Dryand, Psidium guajava L., Malva sylvestris L., Urtica dioica L., and Alcea setosa Alef., against the extracted strains. Methods: The susceptibility of S. typhimurium strains against tested antibiotics was determined using disk diffusion, and the antibacterial activity of medicinal plant extracts was evaluated using well diffusion and broth microdilution assays. Results: The extracted S. typhimurium strains showed high resistance to cephalosporin (100%) and gentamicin (40%); however, all plant extracts examined in this study were influential in inhibiting the growth of the tested strains. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of tested plant extracts ranged from 6.25 to 25 mg/mL and 12.5 to 50 mg/mL, respectively. The most effective plant extracts in inhibiting bacterial growth in the agar well diffusion method were P. guajava, H. sabdariffa, and A. setosa; nevertheless, the most potent bactericidal activity was recorded for M. sylvestris and A. setosa in the broth microdilution method. The examined strains showed 80% and 85% sensitivity to the MBC of alcoholic extracts of M. sylvestris and A. setosa (50 mg/mL), respectively, which is worthy of further exploration by scientists. Conclusions: The results of this study represent the high potency of M. sylvestris and A. setosa extracts as appropriate medicinal and/or food supplements to replace ineffective antibiotics in bird breeding.