Evaluation of Antimicrobial Potential of the Marine Cyanobacterium, Rivularia mesenterica

Background: Antibiotic resistance is becoming a pivotal concern for public health accelerating the search for new antimicrobial molecules from nature. The prevention and treatment of infectious diseases by applying products from marine organisms, especially Cyanobacteria as a potential and promising source of antimicrobial agents appears as a possible alternative.

Aims: To evaluate the in vitro antimicrobial potential of different extracts derived from marine cyanobacterium Rivularia mesenterica against Gram-positive and Gram-negative bacteria, including multidrug resistant bacteria, by comparison with clinically relevant antibiotics.

Methodology: The secondary metabolites were extracted from fresh and dried cyanobacterial biomass in water and different organic solvents. Antimicrobial efficacy of different extracts was evaluated by the disc diffusion assay. Additionally, the minimum inhibitory concentrations (MIC) of the ethanol extracts obtained from fresh and dried biomass was also determined.

Results: The ethanol extracts obtained from fresh and dried biomass of R. mesenterica showed significant antimicrobial activity against five Gram-positive and five antibiotic resistant Gram-negative bacteria and four fungal strains in comparison with the clinically relevant antibiotics. The inhibitory effect of the ethanol extracts was observed, with MIC values in the range 0.06 to 32.00 μg/ml against tested strains. Furthermore, the water extract was inactive against of the tested bacteria and fungi.

Conclusion: These results suggest that the ethanol extracts of R. mesenterica possess potent broad spectrum of antimicrobial activity, which can serve as an interesting source for antimicrobial compounds and promising alternative to synthetic antimicrobial drugs discovery.