文蛤病原菌——需钠弧菌的鉴定和生物学特性分析

Identification and biological characteristics of pathogen Vibrio natriegen from clam Meretrix meretrix

从患病文蛤Meretrix meretrix体内分离出一优势菌株WT01,回归感染试验证明是文蛤的致病菌。对该菌形态、生理生化特征、盐度、温度和pH值生长条件以及16S rRNA基因序列进行了研究。结果表明,该菌为革兰氏阴性菌,发酵葡萄糖产酸不产气,氧化酶阳性,生长需NaCl,无色素,不发光,在TCBS平板上形成圆形黄色菌落,对弧菌抑制剂O/129敏感,具有弧菌属的典型特征。16SrRNA基因序列分析表明,该菌与需钠弧菌Vibrio natriegen的亲缘关系最为接近,其同源性达99%以上。因此,将该菌鉴定为需钠弧菌。实验显示其半数致死量为5.5×106CFU/g。19种抗菌药物药敏试验结果表明,该菌对氟哌酸、复方新诺明、菌必治、先锋必、链霉素、氯霉素和庆大霉素等抗生素较为敏感。并对其胞外产物的生物学特性进行了分析。

A pathogenic bacterium（WT01）was isolated from diseased clam Meretrix meretrix Linnaeu, and was confirmed to be the pathogen of the epidemic by artificial infection experiment. The morphological,physiological and biochemical characteristics and 16S rRNA sequence were analyzed for this bacterium, and the relationship between reproduction of the bacterium and NaCl concentrations, pH and temperature were also determined. The results showed that the strain was gram-negative, glucose fermented without gas production, oxidase positive, requiring sodium ions for growth, no pigment, non-luminescence; It grew well on TCBS-plate as yellow colonies and was sensitive to Vibrio inhibitor O/129. Therefore,it was confirmed that the strain belonged to the genus of Vibrio. The sequence analysis of 16S rRNA gene of WT01 and comparison with that of other related Vibrios showed that WT01 was very close to Vibrio natriegen, with a similarity of 99%. In conclusion,strain WT01 belonged to Vibrio natriege, and the LD50 of the bacterium to M. meretrix was 5.5 × 10^6CFU/g（tested by Reed-Muench method）. The sensitive test showed that the pathogen was sensitive to drugs such as norfloxacin（NOR）, bactrim （ SXT）, ceftria xone （ CRO）, cefobid （CFP）, streptomycin （STR）, chloromycetin （CMP） and cidomycin（GEN）. Biochemical analysis was also done for its extracellular Droducts.