Evaluation of Antibacterial Ability of New Modified Bentonite Compounds Against Aquaculture Pathogenic Bacteria: Aeromonas hydrophila and Streptococcus iniae

The prevalence of bacterial diseases is one of the most important problems facing Iran's aquaculture industry development. Various gram-positive and negative bacteria such as Aeromonas hydrophila and Streptococcus iniae have caused widespread complications in farmed fish.The use of antibiotics causes problems for human consumers. Therefore, the use of new antimicrobial agents with minimal complications is common. In this research, the structure of bentonite clay was modified using a cationic surfactant and acid-thermoactivated method. Structural studies have shown that changes in the bentonite structure have been achieved through two methods. In this study, antimicrobial activity of two types of modified bentonite against Streptococcus iniae and gram-negative bacterium Aeromonas hydrophila was investigated under laboratory conditions using two methods of bacterial growth inhibition (disc method) and test tube (microdilution). In order to determine the antimicrobial activity, the Minimum Inhibitory Concentration and the Minimum Bactericidal Concentration (MIC and MBC) were determined by microdilution and colony count in Meller Hinton agar culture medium. The results showed that the modified bentonite with cationic surfactant had MBC of 42.85 and 28.57 mg/L for Aeromonas hydrophila in 10 minutes and 30 minutes and 71.42 mg/L in 10 and 30 minutes for Streptococcus iniae, respectively. For the thermoactivation bentonite, MBC was 28.57 and 71.42 mg / L for Aeromonas hydrophila, in 10 and 30 minutes respectively, and 28.57 and 14.28 mg / l for 10 and 30 min for Streptococcus iniae. The results of this study showed that modified bentonite compounds  have strong antimicrobial effects against pathogens in laboratory conditions and can be used as new compounds to control pathogens in aquaculture systems used.