Antibacterial Properties of Methanolic and Aqueous Extracts of Some Plants against Some Enterobacteriaceae Species

The extracts of six medicinal plants namely Terminalia chebula fruits, Commiphora myrrha gum, Solenostemma argel leaves, Rutagraveolens aerial parts, Cistanche phelypaea aerial parts and Striga hermonthica stem used in traditional Sudanese medicine for the treatment of gastrointestinal tract infections were selected to evaluate their potential antibacterial activity. The antibacterial activity of methanolic and aqueous extracts of these plants were determined by agar diffusion technique in vitro against 20 clinical isolates (2 were Salmonella typhi, 5 Proteus mirabilis, 4 Escherichia coli, 5 Pseudomonas aeruginosa, 3 Staphylococcus aureus, one was Salmonella paratyphi B) and 5 standard bacterial strains (Staphylococcus aureus ATCC 25923), Bacillus subtilis (NCTC 8236), Escherichia coli (ATCC 25922), Salmonella typhi (ATCC1319106) and Klebsiella pneumoniae (ATCC 35657) at a concentration of 100 mg/ml. Of all plants methanolic and aqueous extracts of T. chebula fruits were the most active with clinical isolates and standard bacterial strains showed relatively high antibacterial activity against most of the tested microorganisms with the diameter of inhibition zones ranging between 20 and 24 mm, whereas the methanolic extract of Commiphora myrrha showed high antibacterial activity against Proteus mirabilis and Escherichia coli clinical isolate (1Z = 20 mm). Solenostemma argel leaves was found moderately effective against S. aureus (ATCC 25923 ((1Z = 18 mm) but did not show any activity against all tested clinical isolates bacteria. Most susceptible Gram-negative clinical Isolates bacteria were Escherichia coli and Proteus mirabilis. Most susceptible Gram negative standard bacteria were Bacillus subtilis (NCTC 8236) and Escherichia coli (ATCC 25922) and least susceptible Gram negative bacterium was Klebsiella pneumoniae (ATCC35657). In Gram positive standard bacteria, most susceptible was S. aureus (ATCC 25923). Antibiotics was used as standards drug for antibacterial assay. The present study reveals potential use of these plants for developing new antibacterial compounds against gastrointestinal tract pathogenic microorganisms.