PDF(Pubmed)
Abstract：
The present study aimed to determine the major cause of the high mortality affecting farmed gilthead seabream (Sparus aurata) and controlling this disease condition. Fifteen diseased S. aurata were sampled from a private fish farm located at Eldeba Triangle, Damietta, fish showed external skin hemorrhages, and ulceration. Bacterial isolates retrieved from the diseased fish were identified biochemically as Pseudomonas putida and then confirmed by phylogenetic analysis of the 16 S rRNA gene sequence. P. putida was also isolated from three batches of tilapia-trash feed given to S. aurata. Biofilm and hemolytic assay indicated that all P. putida isolates produced biofilm, but 61.11% can haemolyse red blood cells. Based on the antibiotic susceptibility test results, P. putida was sensitive to florfenicol with minimum inhibitory concentrations ranging between 0.25 and 1.0 µg mL- 1, but all isolates were resistant to ampicillin and sulfamethoxazole-trimethoprim. Pathogenicity test revealed that P. putida isolate (recovered from the tilapia-trash feed) was virulent for S. aurata with LD50 equal to 4.67 × 107 colony forming unit (CFU) fish- 1. After intraperitoneal (IP) challenge, fish treated with 10 mg kg- 1 of florfenicol showed 16.7% mortality, while no mortality was recorded for the fish group that received 20 mg kg- 1. The non-treated fish group showed 46.7% mortality after bacterial challenge. HPLC analysis of serum florfenicol levels reached 1.07 and 2.52 µg mL- 1 at the 5th -day post-drug administration in the fish groups received 10 and 20 mg kg- 1, respectively. In conclusion, P. putida was responsible for the high mortality affecting cultured S. aurata, in-feed administration of florfenicol (20 mg kg- 1) effectively protected the challenged fish.
摘要：
本研究旨在确定影响养殖金头seabream（Sparusaurata）和控制这种疾病的高死亡率的主要原因。从位于EldebaTriangle的私人养鱼场采样了15个患病的S.aurata，Damietta,鱼表现出外部皮肤出血，和溃疡。从患病鱼类中回收的细菌分离株被生化鉴定为恶臭假单胞菌，然后通过16SrRNA基因序列的系统发育分析进行确认。还从给予S.aurata的三批罗非鱼垃圾饲料中分离出P.putida。生物膜和溶血试验表明所有恶臭假单胞菌分离物产生生物膜，但61.11%可以溶血红细胞。根据抗生素药敏试验结果,恶臭假单胞菌对氟苯尼考敏感，最低抑制浓度在0.25至1.0µgmL-1之间，但所有分离株对氨苄西林和磺胺甲恶唑-甲氧苄啶均具有抗性。致病性测试表明，P.putida分离株（从罗非鱼垃圾饲料中回收）对S.aurata具有毒力，LD50等于4.67×107菌落形成单位（CFU）鱼-1。腹膜内（IP）攻击后，用10毫克千克-1氟苯尼考处理的鱼死亡率为16.7%，而接受20mgkg-1的鱼组没有死亡记录。未处理的鱼组在细菌攻击后显示46.7%的死亡率。在接受10和20mgkg-1的鱼组中，在给药后第5天，血清氟苯尼考水平的HPLC分析分别达到1.07和2.52µgmL-1。总之,P.putida是影响培养的S.aurata的高死亡率的原因，饲喂氟苯尼考（20mgkg-1）可有效保护受攻击的鱼。
