The Effects of Different Solvents on the Growth-inhibitory Activity of Rhazya stricta Extract Against Antibiotic-resistant Escherichia coli

 Escherichia coli (Gram-negative bacilli) inflicts large economic losses on the poultry industry and is one of the most important causes of poultry diseases. The indiscriminate use of antibiotics has contributed to today’s increasing prevalence of drug-resistant strains, which their emergence appears to exceed the discovery of new drugs. Therefore, several attempts have been dedicated to find new compounds as effective alternatives to antibiotics. Medicinal plants constitute a rich source for various antimicrobial compounds.

 The aim of this study was to evaluate the antibiotic resistance trend of the E. coli strains isolated from Quail feces samples and to investigate the antimicrobial effects of Eshvarak extract against these strains.

 Eshvarak plant was collected from Saravan (Sistan and Baluchestan province, Iran) and identified in the botany laboratory of Zabol University. E. coli samples were isolated from poultry feces. Various solvents (methanol (100%), ethanol (100%), water (100%), hydro-alcohol (70%), and ethyl-acetate (100%)) were used to prepare Eshvarak extract. Inhibitory zone diameter was determined in an agar-based medium using a standard procedure. The MIC and MBC of prepared extracts were determined by the micro-dilution method.

 The lowest MIC values were obtained for the methanolic (12.5 ppm), ethanolic (12.5 ppm), aqueous (12.5 ppm), hydroalcoholic (25 ppm), and ethyl-acetate (12.5 ppm) Eshvarak extracts. The highest inhibitory zone diameters against E. coli were recorded at the 100-ppm concentration of the methanolic (8 mm), ethanolic (7 mm), aqueous (8 mm), hydroalcoholic (10 mm), and ethyl-acetate (5 mm) Eshvarak extracts.

 Eshvarak extract, particularly in the hydroalcoholic solvent, inhibited the growth of E. coli. However, the antimicrobial properties of plant extracts seem to be independent of the extraction method or the type of solvent.