Synergistic antibacterial effect of Glycyrrhiza glabra and Rosmarinus officinalis against MRSA isolated from Egypt

Abstract

192 Staphylococcus samples were isolated from patients in Egyptian hospitals and 112 were identified as Staphylococcus aureus using conventional methods based on morphological and biochemical characteristics. Sensitivity of isolates to a range of antibiotics was also tested by disc diffusion method, which revealed that 82% of isolates were MRSA isolates. Methicillin resistance was confirmed using PCR-based molecular approach, 8 isolates were harboured mecA gene and 4 isolates were Borderline S. aureus (BORSA). MICs of different antibiotic classes were determined; results were varied to different antibiotics, where Penicillin and Ampicillin MICs varied from resistant to borderline resistant isolates (512,62?g/ml). Cinnamomum cassia, Syzygium aromaticum, Glycyrrhiza glabra, Rosmarinus officinalis and Salvia officinalis plant extracts were tested to examine their antibacterial activity against MRSA isolates. MIC of tested plant extracts was evaluated by agar dilution method. Diethyl ether extracts of G. glabra, R. officinalis and S. officinalis showed the lowest MICs values (0.05, 0.39, 0.195mg/ml respectively). Investigation of possible synergistic effect upon combination between plant extracts with the lowest MICs values was evaluated by a checkerboard titration assay. Combination between diethyl ether extracts of G. glabra and R. officinalis at conc. 0.0125 and 0.0975 mg/ml respectively showed synergistic effect on MRSA isolates and standard strain. Both extracts shown antibacterial effects on MRSA cells by shrinkage of the protoplasts and disruption of the cytoplasmic membrane evidenced by protein analysis and Microscopic examination of cells pre and post treatment by TEM .These results suggest that these extracts might be used as a promising antibacterial agent.