Role of Aeromonas hydrophila in bacterial septicemia of cultured carps in khuzestan province

    Aeromonas hydrophila is a ubiquitous and opportunistic aquatic microorganism, that conflicting views have been expressed concerning whether Aeromonas hydrophila is a primary pathogen of  freshwater fish or a secondary opportunistic pathogen. Under stress condition, such as temperature changes, handling or poor water quality, this bacterium becomes a pathogen. Aeromonas hydrophila has been associated to the dominant infectious agent of hemorrhagic septicemia in freshwater cultured fishes. In this study, a total of 200 pieces of patient cultured carp (126 common carp, 39 silver carp and 35 grass carp) were taken from Khuzestan province farms. A total of 125 and 31 isolates were identified as Aeromonas sp. and Aeromonas hydrophila respectively by biochemical methods and PCR analysis by specific primers such as 16srRNA for aeromonas sp., and 16srRNA and lipase for detection of Aeromonas hydrophila. The results showed that Aeromonas sp. and  Aeromonas hydrophila are responsible for 62.5% and 15.5% of carp septicemia respectively and prophylactic measures should be considered.  It also concluded that PCR assay provides a highly sensitive and specific tool for the detection of  Aeromonas hydrophila compared with  biochemical methods.