Investigation of Antibacterial Activity of Ethanolic and Methanolic Extracts of Mentha pulegium L

Background: With regard to the rapid emerging antibiotic resistance bacteria, plants as one of the most common natural sources of antimicrobial agents can be used as alternative for treatment of infectious diseases. This study was designed to investigate antibacterial activity of Mentha pulegium L. (Lamiaceae family). Materials and Methods: In this experimental study, the antibacterial effect of 4, 8, 16 and 24 mg/disc of alcoholic extracts were assessed using standard disc diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also determined. Furthermore, the structural changes following to the exposure with these extracts were also investigated in test bacteria. Results: Both extracts of this plant showed considerable antibacterial activity against some Gram positive (Bacillus cereus and Staphylococcus aureus) and also Gram negative (Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis) bacteria. All of the tested bacteria were resistant to nafcillin. The maximum effects was observed in the case of both ethanolic and methanolic extracts in all concentrations on P. mirabilis (25 mm) and the lowest effect was on P. aeruginosa. MIC and MBC values of both extracts against S. aureus were equal (MIC=MBC=8 mg/mL) and P. mirabilis were MIC=4 mg/mL and MBC=8 mg/mL. The SEM analysis revealed deformation and cell wall disruption of affected bacteria. Conclusion: Based on these results it can be suggested that M. pulegium L. is an effective antibacterial plant that can be used as a new source for antibiotic discovery against bacterial pathogens especially food poisoning pathogens such as S. aureus, B. cereus and also for treatment of P. mirabilis infection.