4种微生物DNA对罗非鱼抗海豚链球菌感染的初步研究

Effect of Injecting Four Kinds of Microbial Genomic DNA on Resistance of Tilapia(Oreochromis niloticus) against Streptococcus iniae

将4种微生物基因组DNA腹腔注射罗非鱼(Oreochromis niloticus),48 h后腹腔注射海豚链球菌,在攻毒后24和48 h采血,通过测定血清溶菌酶(LSZ)、超氧化物歧化酶(SOD)和碱性磷酸酶(AKP)活性的变化,以及血液中病原菌感染量和死亡率,探讨注射4种微生物DNA对罗非鱼抗海豚链球菌感染的作用。结果显示,注射大肠杆菌DNA的实验组,LSZ、AKP和SOD均无明显变化(P>0.05),表现为先略低于对照组后升至正常水平;而注射鮰爱德华氏菌DNA、毕赤酵母DNA和生理盐水的实验鱼,LSZ和AKP表现出明显变化(P<0.05),LSZ变化趋势为先增加后降低,而AKP变化趋势则不同。注射感染后除对照组外,其他处理组均有不同程度的细菌感染,其中24 h大肠杆菌组感染量显著低于生理盐水组(P<0.05),而48 h各试验组的细菌感染量均显著低于生理盐水组(P<0.05),尤其以大肠杆菌组和嗜水气单胞菌组最低,且其死亡率也最低,表明注射一定量的大肠杆菌基因DNA和嗜水气单胞菌基因DNA能增强罗非鱼抗海豚链球菌感染能力。

The genomic DNA extracted from 4 microbe was used for intramuscular injection the tilapia,Oreochromis niloticus,48 h later the tilapia were infected by S.iniae and then sera were collected at 24 and 48 h.The effect of injecting four kinds of microbe on the resistance of tilapia against S.iniae was determined by measuring their Lysozyme activity,Superoxide dismutase activity,Alkaline phosphatase activity and the pathogenic number infected in the serum,then the mortality rates.The results showed,the changing scale of the activity of three enzymes of the group（Escherich coli） was small.At the 24 h of post-infection,serum enzymes level was lower than the control and at the 48 h recovered the normal.But the LSZ activity of the groups（Edwardsiella ictaluri,Pichia pastoris and 0.85 % NaCl） first increased then decreased in 48h after the injecting of S.iniae and their changing scale was big,and the AKP activity was different.Besides the control,all the treatment groups had more or less pathogenic quantity in the serum after challenged with S.iniae;At the 24 h of post-infection,the infection quantity of the group（Escherich coli） significantly lower than 0.85 % NaCl（P〈0.05）,yet at the 48 h of post-infection,the infection quantity of all the treatments were significantly lower than 0.85 % NaCl（P〈0.05）,especially the lowest value at the groups（Escherich coli and Aeromonas hydrophila）.The mortality rates of the groups（Escherich coli and Aeromonas hydrophila） were lower than other treatments.Therefore,the results indicate that the genomic DNA of Escherich coli and Aeromonas hydrophila could enhance the non-specific immune response and resistance to potential infection to tilapia.So it was a potential type of immunostumulant for tilapia.