Preparation And Application Of Bacteriophage Agent For Controlling Vibrio Alginolyticus Infection In The Turbot

Turbot?Scophthalmus maximus L?is an economically valuable fish mainly cultured in the coastal areas of north China.However,with the development of turbot farming industry,the bacterial diseases caused by vibrio are becoming more and more serious.Bacteriophage,a natural bacteriostatic agent,is green,safe and environmentally friendly.Compared with traditional antibiotic drugs,it has the advantages of no drug resistance,no residue and no pollution to the environment.In this study,phage PVA1 was taken as the main research object to investigate its therapeutic effect and safety,and a phage agent of PVA1 that could be preserved at room temperature was developed and its application effect was evaluated.The main research contents are as follows:?1?The pathogenicity of Vibrio alginolyticus on turbot was verified,and the treatment effect of vibriosis caused by V.alginolyticus was investigated.LD₅₀ of turbot infection by V.alginolyticus by immersion is 7.85?10⁶ CFU/mL,LD₅₀ of turbot infection by V.alginolyticus by intraperitoneal injection is 1.52?10⁶ CFU/g.MOI?10 is the best concentration for the treatment of immersion bath challenge.The result of challenge therapy with intraperitoneal injection was MOI?10.?2?The results of acute and chronic intraperitoneal phage PVA1 challenge showed that PVA1 injected into the abdomen at 100 times the treatment concentration in the acute challenge did not cause the death of turbot in a short period,and no LC₅₀ of PVA1 was detected.The survival rate,body weight and length of turbot were not significantly affected by1 month chronic intraperitoneal injection.The plasma biochemistry,liver,kidney and spleen cells of turbot were not significantly affected.?3?The effect of allicin on phage preservation at room temperature was studied.The phage preparation of V.alginolyticus was developed,which was formulated as 4.32?10⁷PFU/mL PVA1,0.1250 mg/mL allicin,2.5 mmol/mLNaCl and 5.0 mmol/mL MgCl₂.The results showed that the survival rate of turbot was 70.00%in the phage preparation group and76.7%in the Doxycycline group,there was no significant difference in survival between the two groups.