Antibacterial effect of the brown alga Cystoseira trinodis
It is understood that bacteria can become resistant to the existing antibiotics. Thus, finding the new antibacterial substances is an important necessity. Since algae have been known to contain biologically active compounds, in the present investigation we attempted to study of antibacterial effect of the brown alga Cystoseira trinodis harvested from the Persian Gulf. This investigation was an in vitro study. The activity of the extract of C. trinodis was examined against Staphylococcus aureus (ATCC 25923), Staphylococcus epidermidis (ATCC 14990), Escherichia coli (ATCC 25922), and Pseudomonas aeruginosa (ATCC 27853). The minimum inhibitory concentration (MIC) of the extract was determined for each test strain. Extract of C. trinodis showed antibacterial activity against all test organisms. The MIC of extract was 1.031 mg/ml for S. aureus, 0.687 mg/ml for S. epidermidis, 4.125 mg/ml for E. coli, and 6.6 mg/ml for P. aeruginosa. The extract was active against both gram-positive and gram-negative species which were tested in this study. C. trinodis could be a useful natural resource for preparation of antibacterial agents.