In Vitro Antibacterial Activity of Rheum ribes Extract Obtained from Various Plant Parts Against Clinical Isolates of Gram-Negative Pathogens

Rheum ribes is among the Polygonaceae family which is endemic in Iran and a few neighboring countries. In this investigation, antibacterial effects of root, stalk and leaves extracts of Rheum ribes on a few common clinical isolates of gram negative pathogens were studied, using the cup plate and paper disc methods. Gram negative microorganisms studied were Escherichia coli, Klebsiella pneumoniae, Proteus spp., Pseudomonas aeruginosa and Neisseria gonorrhoeae. For examination of pathogenic microorganisms in the cup plate and disc diffusion method, methanolic extracts of different plant parts at concentrations of 250 and 500 micrograms per cup or disc, were used. The root and leaves extracts have demonstrated significant antibacterial activities in both methods. However, stalk extracts showed a lower degree of antibacterial activity than the root and leaves extracts. Generally, the extracts showed a broad spectrum of activity, although they were more effective against P. aeruginosa and Proteus spp. in comparison with the positive control. The results suggested that extracts of Rheum ribes could be effectively used against clinical isolates.