Prevalence and molecular charachterization of Gram negative pathogenic bacteria in rainbow trout from fish farm in Mazandaran province

Background and Aim : The aquaculture industry has evolved dramatically over the last few decades but various infectious diseases threaten aquatic life. Due to increased consumption of marine products, the health of aquatic animals needs constant monitoring. Fishes viscous skin cover is a good place to grow a variety of pathogenic bacteria. The purpose of this study was to isolate and survey the prevalence of Gram-negative bacteria in trout in Mazandaran province.Methods : . Clinical samples of trout in some fish farms of Mazandaran province were collected during year ۲۰۱۹ (from winter to autumn). These farms were selected based on the previous occurrence of bacterial disease. After disinfection of fish body surface with ethanol, samples were taken from the kidneys, liver and spleen of fish. The clinical specimens were inoculated in nutrient agar and incubated at ۲۵ °C for ۴۸ to ۷۲ hours. Colony characteristics, cell morphology, gram staining, biochemical tests and PCR test were performed to identify bacteria.Results : The results were demonstrated that the most contamination with gram-negative bacteria in Mazandaran trout farms, related to Aeromonas hydrophiliae and Yersinia ruckeri (among the identified isolates in the province for Y. ruckeri and A. hydrophiliae) were ۴۰.۹% and ۳۱.۸%, respectively. In addition the high prevalence of bacterial disease was Flavobacterium psychrophilum with ۲۰.۴%. In the clinical samples collected from trout farms in Babol city, F. psychrophilum had the highest prevalence, compared to the clinical fish samples of other citiesConclusion : Therefore, serious measures to prevent and observe health issues, including reducing environmental stress such as food storage health, environmental temperature and transportation conditions in fish farms are important.

Keywords:

Pathogenic bacteria , rainbow trout , fish farm , Mazandaran province