The overuse of therapeutic antibiotics results in the drug resistance. The excessive use of antibiotics causes the mutations in the microorganisms and the emergence of new microorganisms which are resistant against the common antibiotics. With regard to limitations and known side effects of antibiotics, the exploring of antimicrobial compounds seems necessary. The purpose of this study is to evaluate the antimicrobial effects of aqueous and ethanolic extracts of Chevil against Staphylococcus

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... dermidis PTCC 1435, Yersinia enterocolitica PTCC 1221 and Enterobacter aeruginosa PTCC 1151 and to compare them with the common therapeutic antibiotics. Materials and Methods: In this experimental study, after collecting plants from the highlands of Chaharmahal va Bakhtiari province, the extraction was carried out by the maceration method. To evaluate the antimicrobial activity, Disc diffusion test with Kirby-Bauer method was used. The Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentration (MBC) were determined by using the dilution method. Results: The highest inhibition zone diameter in 40 mg/ml was related to Staphylococcus epidermidis and the minimum diameter in this concentration was related to Gram-negative bacteria, Enterobacter aeruginosa. MIC of aqueous and ethanolic extracts for Enterobacter aeruginosa 64 and 32 mg/ml and MBC of ethanolic and aqueous extracts of Enterobacter aeruginosa were 128 and 64 mg/ml respectively. Conclusion: The ethanolic extract of the Chevil compared with the common therapeutic antibiotics had more inhibitory effect on studied bacteria. Furthermore, Chevil extracts showed greater inhibitory effect on Gram-positive bacteria in comparison with Gram-negative bacteria.