Screening and Characterization of Antibacterial Activity of Ecklonia cava Against Listeria monocytogenes

Abstract

In effort to discover alternative antimicrobials against Listeria monocytogenes, methanol (MeOH) extracts from thirteen different marine algae were screened for their antibacterial activity against the aforementioned bacteria by disk diffusion assay. Among all thirteen screened marine algae, Ecklonia cava exhibited the highest antibacterial activity against L. monocytogenes. The evaluation of antibacterial activity of MeOH extracts and its soluble-solvent fractions from E. cava against L. monocytogenes by disk diffusion assay showed that ethyl acetate (EtOAc) fraction has the highest antibacterial activity against L. monocytogenes among all fractions. For both minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests, EtOAC fraction from E. cava exhibited the highest antibacterial activity against L. monocytogenes as evidenced by its smallest MIC value of 256 µg/mL and MBC value of 512 µg/mL. Furthermore, the eventual synergistic effect of EtOAc solvent-soluble fraction of E. cava in combination with streptomycin and gentamycin against L. monocytogenes was investigated. The results showed that EtOAc fraction in combination with gentamycin or streptomycin greatly reduced the MIC values of gentamycin up to 64 times less than its MIC when it was used alone and up to 256 times for streptomycin respectively. The results of the present study indicate that extracts of E. cava are promising sources for the discovery of antimicrobials against L. monocytogenes with potential applications in food industries to control food pathogenic microbes. Thus, further works leading to its purification and elucidation of relevant pharmacological aspects are still needed.