Investigation for antibacterial effect of astaxanthin on Aeromonas hydrophila

The aim of this study is to research antibacterial effect of astaxanthin on Aeromonas hydrophila. A. hydrophila is an important fish pathogen. The agent causes serious economical losses under culture conditions. In the study, sick fish were taken from a commercial fish farm in Antalya in 2017. Six fish samples, weighing 56-225 g and 16.5-24 cm in height were studied. Commercial astaxanthin was used in the study. Antimicrobial susceptibility of the isolated strains in the study were determined by using standard disc diffusion technique. Ampicillin, erythromycin, flumequin, nalidixic acid, oxalinic acid, chloramphenicol, trimethoprim, streptomycine, tetracycline and sulfamethoxazole. To determine antibacterial effect of astaxanthin, different astaxanthin solutions were prepared by using ethanol, methanol, water, chloroform and 2-propanole. Behaviour findings such as lethargy, swim to water surface and anorexia were determined. Externally, darkening of the body colour, abdominal dropsy, exophthalmia, pale gills, lesions on the body surface and loss of scale. Internally, hemorrhagies within mouth, hemorrhagies on the muscle tissue, pale liver, enlarged spleen and lysis of the kidney were determined. In the study, six A. hydrophila strains were isolated and identified. According to the results of the antibiotic sensivity test, it was determined that A. hydrophila strains were resistance to oxytetracycline. It was found that the chloroform solution of astaxanthin was effective.