Detection of Vertical Transmission of the Bacterium Streptococcus Agalactiae in Rainbow Trout (Oncorhynchus Mykiss) Brooders Using the PCR of the Gene Scpb

Streptococcus agalactiae (group B, GBS) is an important human and animal pathogen that causes invasive infection in fish. The present study aims to investigate the detection of vertical transmission S. agalactiae using the PCR of the gene scpB in the ovarian tissues. A group of 48 fishes were injected intramuscularly (i.m) with 0.5 ml bacterial suspension containing 3.5×107 CFU/0.5 ml in normal saline, This group was compared with a control group of 48 fishesthat were injected with 0.5 ml sterile saline. In this study kidney tissue, ovarian tissue and ovarian fluid were sampled from the fourth day after injection. DNA was extracted from both the direct tissue and the bacteria isolated from the tissues, which were cultured in the BHI medium. The extracted DNA was then used in the PCR. The PCR confirmed the existence of this bacterium in 91.46% (44/48) and 68.75% (34/48) of the kidney and the ovarian tissues, respectively, and 95.83% (46/48) and 87.5% (42/48) of bacteria isolated from the kidney and the ovarian tissue cultures, respectively. The presence of S. agalactiaein rainbow trout ovarian tissue was confirmed by PCR and sequencing that can be the evidence for vertical transmission of this bacterium in rainbow trout brood stock.