Molecular and biochemical ‎investigation of the role of ‎streptococcus iniae in mortality of ‎Lates calcarifer cages culturing in ‎the Persian Gulf

Streptococcus iniae is a gram-positive bacterium that causes invasive infections with severe septicemia and meningitis as well as high economic losses in freshwater and sea fish. It is one of the most infectious diseases in Asian sea bass. The purpose of the present study was to investigate the role of this bacterium in marine bass fish mortality in farmed cages on the northern coast of the Persian Gulf.  In this study, a number of 150 cultured Asian sea bass (60 fish suspected of bacterial infection and 90 apparently healthy fish) were selected and bacterial sampling were taken from head kidneys and brain of fish from sea bass cages of Bushehr, Khuzestan and Hormozgan provinces. After isolation and purification of the bacteria, the presence of Streptococcus iniae was evaluated and confirmed via biochemical tests and molecular methods (with specific primers of lctO gene). The PCR results and sequencing of the PCR product indicate high prevalence of Streptococcus iniae in Asian sea bass cages culturing in the Persian Gulf. Therefore, effective measures should be taken to prevent Streptococcosis (especially vaccination).