RESUMEN
Despite the discovery of numerous antibiotics, drug resistance still remains as a major problem. Therefore, it is important to introduce and replace new sources of drug such as medicinal plants with antimicrobial properties. The genus Clematis [Ranunculaceae family] has six species in Iran. Aerial parts of Clematis have been used to cure fever and chronic diseases such as Rheumatism in traditional medicine. In this research, antibacterial activity of ethanolic and methanolic extracts of aerial part in two major species of the genus in Iran [contains C. orientalis and C. ispahanica] were studied. Aerial plant parts were dried in shade, powderized and then ethanolic and methanolic extracts were prepared. Antibacterial activity of the two extracts was measured against six laboratory standard strains including gram positive and gram negative bacteria by disc diffusion. Minimum inhibitory concentrations were also determined using broth microdilution. Results showed that antibacterial activity of methanolic extracts is stronger than the ethanolic one. Also, C. ispahanica has stronger antibacterial activity in comparison to C. orientalis. Gram positive test bacteria showed the most susceptibility to both extracts compared to gram negative organisms. According to antibacterial effects of alcoholic extracts, it seems necessary to diagnose effective antibacterial components to compare results with existed finding and introduce a new trapeutic source