Comparison of antibacterial activity of aqueous and methanolic extracts of Dracocephalum kotschyiboiss against some standard and clinical strains involved in wound infection

Background and Aim : It is necessary to develop new efficient antibacterial agents because of the growing antibiotic resistance as a major public health problem. Medicinal plant extracts have a good antimicrobial potential against the resistant/non-resistant pathogenic bacteria due to their secondary active metabolites such as phenolic compounds. These natural agents are more compatible with the body and have fewer unwanted side effects. The aim of this study was to compare the antimicrobial effect of aqueous and methanolic extracts of Dracocephalum kotschyiboiss aerial parts against Staphylococcus aureus and Pseudomonas aeruginosa as two important bacterial pathogens causing burn wound infections.Methods : Aqueous and methanolic extracts of Iranian Dracocephalum kotschyiboiss (aerial parts) were prepared by maceration and their antimicrobial activity was evaluated by disk and agar well diffusion methods against standard strains of Staphylococcus aureus (ATCC ۲۵۹۲۳) and Pseudomonas aeruginosa (ATCC ۲۷۸۵۳) and their clinical strains isolated from purulent wound secretions. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of extracts were determined using microdilution method.Results : Methanolic extract, unlike aqueous extract, showed good antimicrobial effect on all strains. Methanolic extract showed the most antibacterial effect on clinical Staphylococcus aureus with MDR resistance pattern. The concentration of ۵۰ mg/ml of this extract resulted in an average diameter of growth inhibition zone of ۱۸.۳ and ۱۸.۶ mm against Staphylococcus aureus in disk diffusion and agar well method, respectively. The MIC and MBC of this extract on this bacterium were ۶.۲۵ and ۲۵ mg / ml, respectively. Methanolic extract (۵۰ mg/ml) also showed an acceptable effect on Pseudomonas aeruginosa with an average diameter of growth inhibition zone of ۱۸.۶ and ۱۶.۶ mm in disk diffusion and agar well method, respectively. The MIC and MBC of this extract on this bacterium were ۱۲.۵ and ۲۵ mg / ml, respectively. The aqueous extract had no antimicrobial effect on the strains of this study. Conclusion : Due to the antimicrobial effect observed against both gram-positive and gram-negative pathogenic bacteria, the methanolic extract of Iranian Dracocephalum kotschyiboiss (aerial parts) has great potential for use in the treatment of wound infections, which of course requires further research in this area.