Studies on pathogenesis of extracellular products from pathogenetic bacteria in Penaeus monodon Fabrivius

The extracellular products of Vibrio parahaemolyticus,V.Alginolyticus and Aeromonas hydrophila,which were isolated from diseased Penaeus monodon in Tong'an from June to August 1997,are extracted and investigated.Composition of extracellular enzymes from these three bacteria is detected.Among them,protease and phospholiase,including both acidic phospholiase and alkine phospholiase,are chosen to do quantitative analysis on their activities.These three kinds of the above enzymes extracted from cultures of V.Parahaemolyticus are more active than those of the others.Bacterial extracellular products are used to do lethal experiments by injecting to the healthy P.Monodon.Conforming to the result of activity of protease and phospholiase,lethal action of V.Parahaemolyticus' is the strongest and that of V.Alginolyticus' is the weakest.The pathological variations of dying shrimps' livers in the lethal experiments are observed by transmit electron microscope (TEM).Cells of those shrimps' livers show to be destroyed at different extents,for example,nuclear core of some cells disappeared and nuclear membrane are wrecked,mitochondria ave destroyed,even the whole cell is disintegrated.It is showed that not only extracellular products of these three strains are poisonous and could be mortal to shrimps,but also the activities of protease and phospholiase in extracellular products of pathogen are related to toxicity of these three strains.