Investigation of drug synergistic and antibacterial effects of Mentha longifolia essential oil on Shigella flexneri and Shigella sonnei

Introduction: Microbial infections such as shigellosis are the major health challenge in Iran, especially in Khuzestan province in southwest of Iran. According to the importance of medicinal plants in treatment of many infectious diseases and as a valuable alternative of antibiotics, therefore the main purpose of this study was to evaluate the drug synergistic and anti-bacterial effects of Mentha longifolia essential oil on as a local plant against Shigella flexneri and Shigella sonnei as the main causes of shigellosis. Materials and methods: Essential oil of M. longifolia was extracted from its leaves. Antibacterial effects of essential oil were detected by disk diffusion method through the measurement of the inhibitory zone diameter and micro-broth dilution for determining the minimum inhibitory concentration (MIC) on clinical and standard Shigella flexneri and Shigella Sonneistrains. Results: According to the results of disc diffusion test in Agar, essential oil of M. longifolia, with a 35 mm inhibition zone, showed the greatest antibacterial activity against clinical isolate S. flexneri. MIC=1024 and with concentration of 0.8 mg/ml of essential oil was detected in both of standard and clinical of S. flexneri and S. sonnei strains. The essential oil of M. longifolia showed highest synergistic effect with gentamicin (10 μg) and ampicillin (30 μg) on clinical isolates of S. flexneri. Conclusion: The results of this study indicate that essential oil of M. longifolia only or in combination with antimicrobial agents may be useful in treatment of bacterial infections. Additionally, this component can enhance the effect of some antibiotics and resolved some antibiotic resistance problems.

Keywords:

Mentha longifolia , Essential oil , Shigella flexneri , Shigella sonnei