The antibacterial and synergistic potential of some Palestinian plant extracts against multidrug resistant Staphylococcus aureus

Abstract

The present study was designed to screen in vitro antibacterial and synergistic activity of Allium sativum, Ecballium elaterium, Pelargonium graveolens, Rosmarinus officinalis, Phagnalon rupestre & Ruta graveolens plants against multidrug resistant Staphylococcus aureus. The active compounds were extracted from the dried aerial parts of plants with aqueous, 80% ethanol and methanol solvents by using Soxhlet extractor, and essential oils (EOs) which extracted from the fresh aerial parts of plant by using steam distillation. All extracts were screened for their antibacterial activity and synergistic effect in combination with known antimicrobial agents by using the disk diffusion method. The results revealed that, the average diameter of inhibition zones that resulted from the effect of plant extracts against the tested bacteria ranged from 8.33 to 12.66 mm, 10.66 to 13.33mm, 8.33 to 14.66 mm and 8.33 to 12.66 mm for aqueous, ethanol, methanol & EOs extracts, respectively. The extracts that showed antibacterial activity were subjected to minimum inhibitory concentration and minimum bactericidal concentrations assay; a micro-broth dilution assay was performed on 96-well plates using 2, 3, 5-Triphenyl Tetrazolium Chloride (TTC) as an indicator for bacterial growth. The average minimum inhibitory concentrations (MICs) values ranged from 12.5 to 25 mg/ml, 1.562 to 25 mg/ml, 1.562 to 25 mg/ml & 25to 50 μl/ml for aqueous, ethanol, methanol & EOs extracts, respectively. While minimum bactericidal concentrations (MBCs) values ranged from 50 to > 200 mg/ml, 100 to > 200 mg/ml, 25 to 200 mg/ml & 100 to > 200 μl/ml for aqueous, ethanol, methanol & EOs extracts, respectively. Synergistic activity of the plant extracts EOs when combined with antibiotics had different degree of synergism against S. aureus. The results indicated that the possibility of concurrent use of these antimicrobial drugs and plant extracts in combination in treating infectious diseases caused by MDR S. aureus.