The Effect of Withania somnifera Extract on Drug Resistant Strains of Escherichia coli

Abstract

Background: Due to the increased resistance of pathogenic bacteria even towards new antibiotics, researchers have attempted to find herbal antimicrobial agents to replace chemical drugs. Objectives: The purpose of this study was to evaluate the effect of W. somnifera extracts on drug resistant E. coli strains isolated from clinical samples. Materials and Methods: We studied all drug resistant strains of E. coli collected from patients with urinary tract infections hospitalized at Zabol hospitals from January 2010 to January 2012. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of plant extracts were determined by the dilution method with various concentrations of the bacteria. Sensitivity to multiple antibiotics was defined by the Kirby-Bauer disc diffusion test. Results: The results showed that the isolated E. coli strains were sensitive to these antibiotics: erythromycin (52.94%), tetracycline (76.47%), ceftazidime (41.17%), cefixime (35.29%), penicillin (76.47%), ampicillin (58.82%) and nalidixic acid (41.17%). Examination of the herbal extracts showed that the highest maximum inhibitory concentration (MIC) against drug resistant E. coli was 200 ppm. The lowest MIC was 50 ppm, where three strains of E. coli were inhibited at this concentration. Conclusions: Our results indicated that Withania somnifera extracts had antibacterial effects on drug resistant E. coli strains isolated from clinical samples. Further studies are required to evaluate the effective compounds of this plant on microbial agents.