In vitro antibacterial activity of selected plant extracts against Escherichia coli and Staphylococcus aureus bacterial strains

Escherichia coli (E. coli) ATCC 25922 and Staphylococcus aureus (S. aureus) ATCC 29213 have been reported to exhibit resistance to commercial antibiotics worldwide. This study investigated plant-based alternatives to antibiotics against E. coli ATCC 25922 and S. aureus ATCC 29213. Six plants (Astragalus sarcocolla, Commiphora myrrha, Salvia officinalis, Cuminum cyminum, Ziziphus spina-christi, and Hibiscus sabdariffa) were selected based on their traditional use in Saudi Arabia. Ethanolic extracts of these plants were prepared to perform disk diffusion on Muller–Hinton agar. Two experiments were conducted. In the first experiment, filter paper discs impregnated with the extracts were placed on E. coli and S. aureus culture plates and then incubated at 37 °C for 18–24 h. Based on the initial screening results, a second experiment was conducted to determine the most effective dose. Hibiscus sabdariffa and S. officinalis exhibited the most significant (P < 0.001) antibacterial activity among the tested plants. Hibiscus sabdariffa demonstrated significant antibacterial activity against E. coli and S. aureus, with mean inhibition zones of 15.0 mm (± 4.2 SD) and 8.11 mm (± 1.5 SD), respectively, while S. officinalis showed mean inhibition zones of 29.5 mm (± 8.4 SD) and 26.33 mm (± 9.9 SD) for E. coli and S. aureus, respectively. Higher concentrations (50 mg/ml and 30 mg/ml) of S. officinalis and H. sabdariffa showed greater antibacterial activity than the 5 mg/ml concentration. These findings suggest the potential of S. officinalis and H. sabdariffa as natural remedies to combat bacterial infections.