Background and Objectives: Today, the increasing failure of chemotherapy and antibiotic resistance displayed by pathogenic bacteria infectious agents have caused the screening of new secondary metabolites with various chemical structures of marine crustaceans, molluscs and echinoderms with desirable antibacterial activity. This study was designed to determine the antimicrobial effect of muscle wall methanol and acetone extracts of four species of sea cucumber (Holothuria arenicola, H. leucospilota, Stichopus hermanni, S.horrens) in Chabahar coasts on some rainbow trout (Oncorhynchus mykiss) pathogenic bacteria (Lactococcus garvieae, Aeromonas hydrophila, Yersinia ruckeri and Streptococcus iniae).
Methods: An experimental study was conducted at in vitro conditions. Experimental variables include sea cucumber species, different concentrations of extracts and bacterial strains. After preparing extracts of mentioned sea cucumber by maceration method, the antimicrobial effect of outcome extracts from their muscle wall were investigated by two different methods: disk diffusion and well diffusion
Findings: At acetone extract of S.horrens, the highest growth inhibition zone for Y. ruckeri and A. hydrophila bacteria at 12 mg/mL concentration in disk diffusion method (11.10 and 13.03 mm) were seen respectively. Different concentrations of methanol extract of S. hermanni, H. leucospilota and H. arenicola were inactive on the tested bacteria. While, Minimum Inhibitory Concentration (MIC) of acetone extracts of S.horrens for Y. ruckeri and A. hydrophila was 0.625 and 1.25 mg/mL respectively and Minimum Bactericidal Concentration (MBC) for Y. ruckeri and A. hydrophila bacteria were 2.5 and 2.5 mg/mL respectively in well diffusion method.
Generally, it type of extract, sea cucumber species and also bacterium strain are influenced on growth inhibition zone, MIC and MBC. Acetone extract of S. hermanni and S. horrens sea cucumbers can prevent the growth of Y.ruckeri bacterium tested by both methods (disk diffusion and well).