Aeromonas Hydrophila In The Siberian Sturgeon Tissue Distribution And The Resulting Pathological Changes

The essay systematically analysed the distribution of pathogenic bacteria in tissue and the infected histopathological changes in Acipenser baerii infected with Aeromonas hydrophila isolates (SAH-1). The results showed there was interrelationship between the disposition and the infected pathological damages.40 Acipenser baerii (500g±20g) were infected with SAH-1 through peritoneal injection and bacterial soaking while 10 normal sturgeons were performed as negative control. The clinical symptom was observed. Acipenser baerii of each group were dissected after infection at 12h,18h,24h,48h,72h respectively. The samples were carried out through the gross lesions, histopathological and cytopathological observation.The Acipenser baerii of injected and immersed group showed apparent clinical symptoms in late experiment period. The sick fish was abdominal swelling. The bleeding and ulcer was showed around anus, eyes and the base of ganoid scale as well as inflamed anal and bloody water outflow. Liver, spleen and kidney became intumescent, soft and dark red. Mesentery and gonad had the hemorrhage spots. Intestine had gray mucus and no food. Besides, the hindgut bleeded severely.Histopathological observation showed that the heart, spleen, kidney, liver, intestine, muscle, stomach, gonads and other organs were hyperemia, hemorrhage, degeneration, necrosis. Charateristic lesions included actue nephrities, myocardities, enteritis and hemorrhagic inflammatory splenitis. Endothelial cell swelled at liver and intestinal blood vessels.Cytopathological observations showed that mitochondrial swelled at skeletal muscle, heart muscle, spleen lymphocytes, hepatocyte, renal tubular epithelial cells; cristae ruptured or dissolved; mitochondria was empty and endoplasmic reticulum expanded; myofibril ruptured, dissolved or disappeared; SAH-1 gathered in cytoplasmic of renal tubular epithelial cells.The results of immunohistochemical detection were as follows:Injection group:There was no positive signal at 12h post-infection; positive signals were first appeared in the heart, spleen, kidney, liver at 18h and 24h post-infection; positive signals appeared at the gut, muscle, stomach and gonad at 48h post-infection. Immersion group:There was no positive signal in each tissue at 12h and 18h post-infection; positive signals were first appeared in the heart, spleen, kidney, liver at 24h post-infection; positive signals appeared at the gut, muscle, stomach and gonad at 48h post-infection and the positive signals were mainly located in the cytoplasm of infected cells, and occasionally appeard in the intercellular substance. Aeromonas hydrophila first infected cardiac muscle, spleen, kidney, liver, intestines and other organizations, and then extended to the muscle and gonad while the brain tissue had no detected positive signals during the whole infection.The results of Aeromonas hydrophila distribution in sturgeon tissue and pathological changes of experimental infection group showed that the there was positive correlation between the distribution of Aeromonas hydrophila in the Siberian sturgeon and the infected pathological damage.