Antibacterial and synergistic effects of Kochia scoparia extracts against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is serious clinical urgent problems worldwide. Few new drugs are available against methicillin-resistant S. aureus (MRSA), because MRSA has the ability to acquire resistance to most antibiotics, which consequently increases the cost of medication. In the present study, the antibacterial activity of Kochia scoparia was investigated. The antibacterial activities of EtOH extract of K. scoparia and its n-hexane, EtOAc, n-BuOH and water fractions were evaluated against 15 strains of methicillin-resistant S. aureus (MRSA) and 1 standard methicillin-susceptible S. aureus (MSSA) strain by using the disc diffusion method, minimal inhibitory concentrations (MICs) assay, colorimetric assay using MTT test and checkerboard dilution test under dark. Antimicrobial activity of n-hexane fraction of K. scoparia was remarkable. Against the 16 strains, the disc diffusion test was in the range of 15-18 mm, the minimum inhibitory concentrations (MICs) were in the range of 7.8 to 31.25 mu g/ml and FICI values for n-hexane fraction of Kochia scoparia+AM and n-hexane fraction of K. scoparia+OX were 0.31 to 0.75 and 0.12 to 0.37 showing the increase of synergistic effect.