Effects of Escherichia coli strain Nissle ۱۹۱۷ on arsenic-challenged goldfish (Carassius auratus): histological evidence

Arsenic (As) contamination in natural water resources has become a great disaster throughout the world posing serious health problems. The current study was performed to evaluate the protective effects of Escherichia coli strain Nissle ۱۹۱۷ (EcN) against As exposure in goldfish (Carassius auratus). Fish were fed three times a day with ۴.۰۰% of body weight of diet with different doses (۰.۰۰, ۱.۰۰ × ۱۰۶, ۱.۰۰ × ۱۰۷ and ۱.۰۰ × ۱۰۸ CFU g-۱) of EcN for ۸۰ days and then, challenged with ۲۰.۰۰ mg L-۱ As for ۹۶ hr under stagnant flow. Physicochemical characteristics of the inlet water were temperature of ۲۵.۱۰ ± ۰.۷۰ ˚C, pH of ۷.۳۰ ± ۰.۲۰ and dissolved oxygen of ۷.۳۰ ± ۰.۳۰ mg L-۱ and ۵۰.۰۰% of water was exchanged once a week. Afterwards, fish were euthanized with a clove oil solution (۵۰.۰۰ μL L-۱) and tissues were dissected from each fish and immediately fixed in ۱۰.۰۰% buffered formalin. The histopathological results indicated that the supplemented EcN did not have any side effects on various organs. It was also observed that the damages to kidney, liver, gill and skin were pronounced in fish exposed to As. However, the histopathological damages induced by As in fish tissues were less pronounced in the EcN-treated groups compared to the fish fed with the basal diet. Lamellar blood congestion in gills and epidermal cells detachment from the skin surface as well as hepatocytes, enterocytes and tubular necrosis were reduced in treated groups. These findings indicate that EcN has the potential to ameliorate the As-induced organ toxicity.

Keywords:

Arsenic , Escherichia coli strain Nissle ۱۹۱۷ , Goldfish , Histopathology , Probiotics