Determination of Antimicrobial Activity and MIC Value of Tannic Acid Against Four Different Fish Pathogens

In this study, the antimicrobial susceptibility of Silvafeed TSP (tannic acid) obtained from chestnut tree using natural extraction method and used as a feed sweetener in aquaculture against some fish pathogens was investigated. Antimicrobial susceptibility of different concentrations of tannic acid was determined against fish pathogens that cause significant economic losses by bacteria such as Aeromonas hydrophila, Pseudomonas fluorescens, Yersinia ruckeri and Vibrio anguillarum. According to the antimicrobial test results, it was determined that all isolates to tested antibiotics were resistant to ampicillin, however, all isolates were susceptible to other antibiotics except for P. fluorescence isolate. It was determined that the P. fluorescence isolate was resistant to other antibiotics except gentamicin and doxycycline. According to the antimicrobial susceptibility test results of tannic acid against E. coli and four different fish pathogens, P. fluorescens and V. anguillarum were found to be sensitive above 125 µg/ml concentrations. In the same study, E. coli, A. hydrophila, and Y. ruckeri were found to be sensitive above 250 µg/ml concentrations. It was determined that P. fluorescens and V. anguillarum were resistant to tannic acid concentrations below 62.5 µg/ml. Moreover, E. coli, A. hydrophila, and Y. ruckeri were resistant to tannic acid concentrations below 125 µg/ml.