Antibacterial activity of ethanol extracts of seaweeds against fish bacterial pathogens

Crude extracts were prepared using the solvent ethanol from the seaweeds viz., Gracilaria edulis, Calorpha peltada and Hydroclothres sp. and screening for their antibacterial activity against six bacterial pathogens were also carried out. The test bacterial strains were Escherichia coli, Enterobacter aerogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus faecalis and Bacillus cereus. Ethanol extract of Gracilaria edulis inhibited growth of all the test organisms except Bacillus cereus and Enterobacter aerogenes. Seaweed extract of Calorpha peltada was found effective against a number of Gram negative and Gram positive bacteria such as Escherichia coli, Staphylococcus aureus and Streptococcus faecalis. Hydroclothres sp. extract inhibited the growth of Pseudomonas aeruginosa only out of the six tested pathogens.