| Vibrio parahaemolyticus, a kind of Gram-negative bacterium, widely exists inseawater, seabed sediments and marine organisms such as fishes and shellfishes. Itcan infect shrimps, fishes, clams, oysters and so on, so it has brought huge economiclosses to the fishery industry, and caused a great threat to the development ofmaricluture. In addition, it is a common pathogenic bacterium of food poisoning. V.parahaemolyticus-induced food poisoning has showed a rising trend and the infectionhas become a leading factor of foodborne disease in the microbial food poisoning atcoastal areas. If the seafood contaminated by a large number of V. parahaemolyticusand without good processing was consumed, food poisoning would occurred.Infection with V. parahaemolyticus often leads to acute onset, vomiting, abdominalpain, diarrhea and watery stools.In order to explore an effective method of controlling V. Parahaemolyticus,phage qdvp001was isolated and identified from aquatic sewage water with V.Parahaemolyticus (ATCC17802) as host cell, and its physiological characteristicsand preliminary application in oyster purification were also studied. It laid thefoundation for shellfish purification with phages.Phage qdvp001was isolated, identified and purified by double-layer agar platemethod with V. Parahaemolyticus (ATCC17802) as host cell. Its titer could reach to109pfu/ml after liquid or solid proliferation assay. The plaques of the phage qdvp001were round and clear in the center with weak halo on the edge. It was a strong lysisbacteriophage and a good material of the next study.The biological characteristics of qdvp001indicated that the phage had a strongendurance of temperature below60℃, and sensitive to temperature above70℃.Moveover, qdvp001remained high lysis activities in a range of pH4to12and the optimum pH value was8. The optimum MOI value of qdvp001was0.0001, the latentperiod and lytic period was20min and70min, respectively.Electronic microscope showed that the phage had an iosahedral head ofdiameter79nm and a tail of118nm, belonging to the Myoviridae family. SDS-PAGEprofiles indicated that qdvp001contained5capsid proteins, the molecular weight ofthe main capsid protein was estimated at35KD. DNA sequences were obtained andsubjected to blast analysis in NCBI. Compared with those reported information inNCBI, phage qdvp001showed low homology with others，so that it was a novelbacteriophage.In the preliminary application of oyster purification, the number of V.Parahaemolyticus in both oyster farming environment and oyster body were alldecreased after the phage was poured into the seawater，the concentration of V.parahaemolyticus could decrease from1.0×108cfu/ml and1.0×106cfu/ml to3.2×103cfu/ml and2.05×103cfu/ml respectively in oyster farming environment, atthe same time the concentration of V. Parahaemolyticus decreased obviously inoyster body.In short, we had separated a kind of new phage, it was a stronglysisbacteriophage and had strong tolerance to physical and chemical factors. In addition ithad significant scavenging effection on Vp17802in both oyster farming environmentand oyster body. This study provided the theory support to shellfish purification. |
