Antibacterial Effect of Matricaria chamomilla Alcoholic Extract against Drug-Resistant Isolates of Staphylococcus aureus and Pseudomonas aeruginosa

Background: This study aimed to determine antibacterial activity of ethanolic extract of Matricaria chamomilla (chamomile) against methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant (MDR) Pseudomonas aeruginosa strains isolated from clinical specimens. Materials & Methods: The plant samples were collected, and the flowers and leaves were separated and dried completely in the shade. After grinding, extraction was performed using the maceration method. The extracts of both flowers and leaves were dried at ۳۷°C for ۲۴ hrs. About ۵۰۰ mg of the dried plant extract was dissolved in ۱۰ mL of ۵% dimethyl sulfoxide and sterilized by filtration through a ۰.۴۵ µm membrane filter. For the antibacterial assay, agar well diffusion and broth microdilution methods were used. Findings: No inhibitory effect was observed for both extracts against MDR P. aeruginosa isolates in agar well diffusion method. In broth microdilution method, the leaves extract showed inhibitory effect, and its MIC and MBC were determined at ۱۲.۵ and ۲۵ mg/mL concentrations, respectively. The flowers extract showed antibacterial activity against most MRSA isolates. The extract of leaves demonstrated inhibitory effect on ۷ MRSA isolates. The MIC and MBC of flowers extract were determined at concentrations of ۶.۲۵ and ۱۲.۵ mg/mL for most MRSA isolates, while MIC and MBC of leaves extract were ۱۲.۵ and ۲۵ mg/mL for a few MRSA isolates, respectively. Conclusion: In this study, the ethanolic extract of chamomile leaves showed antibacterial activity against MDR P. aeruginosa isolates; meanwhile, the flowers extract showed better activity against MRSA isolates.