بررسي بروز استرپتوكوكوزيس و شناسايي باكتري هاي مسبب آن در مزارع منتخب تكثير و پرورش قزل آلاي رنگين كمان استان مازندران

Evolution of incidence and identification of bacteria agents Streptococcosis in elected Rainbow trout {Oncorhynchus mykiss) farms in Mazandaran province in Iran

The aim of study is evaluation of Streptococcosis incidence and identification of gram positive bacteria pathogen on elected rainbow trout farms in Mazandaran province. Bacterial infections are one of the most important diseases that causing high mortality and economic loss in rainbow trout farms. Therefore, identification of pathogen Bacteria is one of the most important procedures for control and prevention from incidence of bacterial diseases. Some of the gram positive bacteria cocci shape such as Streptococcus and Staphylococcus are hazardous for fish. Mazandaran is one of the most important propagation and culture rainbow trout in Iran and for this result, identification pathogen factors in fish is important in Mazandaran. In this study , 12 farms were selected from 5 cities including 3 farms in Tonekaboun (Dohezar), 1 farm in Chalous (Marzan abad), 1 farm in Noshahr (Kojour), 6 farms in Amoul (Haraz) and 1 farm in Sari (Dodangeh) four season duration , from 2006 (fall and winter) to 2007(spring and summer). For sampling 10 fishes were selected from each farm with clinical sings such as lethargy, darkening, exophthalmia, hemorrhages around the eye and base of the fins .Gram positive cocci bacteria were isolated from the cultures of kidney and liver. Bacteria were cultured in Blood agar or TSA agar plates. Identification of isolates was conducted by staining and biochemical tests. Streptococcosis were shown in Sari, Amoul and Chalous in fall, spring and summer but no gram positive bacteria were isolated in winter. The isolated species were including Streptococcus iniae, Streptococcus agalactiae and Entrococcus faecalis. Results were shown that 33.33 % of infected fish were suffering from Streptococcosis.