Antibacterial Efficacy of Some Medicinal Plants on Multidrug Resistance Bacteria and Their Toxicity on Eukaryotic Cells

The aim of this study was to evaluate the in vitro antimicrobial activity of medicinal methanolic plant extracts against multidrug-resistant bacteria to determine the cytotoxicity of these extracts on eukaryotic cells, and to confirm their efficacy against Methicillin-Resistant Staphylococcus aureus (MRSA) in experimental animals. The effects of the methanol extract of sixty folk plants were investigated on; MRSA, Extended Spectrum Beta-Lactamase E. coli and MDR Pseudomonas aeruginosa by disc diffusion and MIC assay. Cytotoxicity was determined using MTT and hemolysis of human erythrocytes. Three plant extracts with the highest antimicrobial activities were tested using a challenge experiment on mice. Systemic infection was performed by intraperitoneal inoculation of (5 x 10(6) CFU/mL) of MRSA isolate. Then mice received 300 mg/kg body weight of the plant extracts daily for seven days. The efficacy of plant extracts was evaluated by general health, mortality rate, gross lesion, and histopathology study of inoculated mice. Only ten plants showed activities against different MDR bacteria with inhibitory zones ranging from (8 to 22 mm) in diameter. Of the ten medicinal plant extracts, Camellia sinensis and Aloysia citrodora showed the highest activities against MRSA and MSSA isolates, with MIC value ranging from 0.5 to 1.5 mg/ml, followed by Hibiscus sabdariffa, Thymus vulgaris, and Glycyrrhiza glabra. Furthermore, the extract of the effective plants showed low toxicity against Vero and fibroblasts cell lines, along with inhibitory activities to erythrocytes membrane disruption. The in vivo study demonstrated that Camellia sinensis showed significant activity against MRSA infections in mice. The results validate that these plants are effective and safe antibacterial agents against multidrug-resistance bacteria, and have the potential to be utilized as an alternative to antibiotics for the treatment of bacterial infections.