Journal of Tropical Oceanography ›› 2010, Vol. 29 ›› Issue (5): 103-110.doi: 10.11978/j.issn.1009-5470.2010.05.103cstr: 32234.14.j.issn.1009-5470.2010.05.103

• Marine biology • Previous Articles     Next Articles

Isolation and identification of two bacterial pathogens from mixed infection mud crab Scylla serrata and drug therapy

XIA Xiao-an1, WU Qing-yang1, LI Yuan-you1, WANG Shu-qi1, YOU Cui-hong1, LIN You-shun2   

  1. 1. Guangdong Provincial Key Laboratory of Marine Biology, Shantou University, Shantou 515063 China; 2. Shantou Dashun In-dustry Co., Limited, Shantou 515000 China
  • Received:2008-08-04 Revised:2009-12-07 Online:2010-10-30 Published:2011-10-10
  • Contact: 李远友。 E-mail: yyli@stu.edu.cn
  • About author:夏小安(1982—), 男, 江西省新余市人, 硕士, 主要从事水产动物病害学研究。E-mail: xia1982817@163.com
  • Supported by:

    广东省科技计划重大专项(2006A36502004)和农业攻关项目(2008B020800004);广东高校产学研结合示范基地科技成果转化重
    大项目(cgzhzd0812);广东省教育部产学研合作专项资金项目(2007B090400049);广东省海洋渔业科技推广专项(A200905J01)

Abstract:

Two preponderant bacterial strains were isolated from the infected mud crab (Scylla serrata) in Niutianyang aqua-culture area of Shantou. One displayed yellow color and the strain was named as HY, the other showed green color and the strain was named as HG after growing on the TCBS agar plate. Both of them were rod shape and displayed gram negative. After healthy S. serrata individuals were infected with HY or HG by intramuscular injection, obvious histopathological changes could be observed in their tissues as those in the naturally diseased S. serrata, which lead them to their death. These results demonstrate that both HY and HG are pathogens of S. serrata. With the total HY or HG DNA as a template and bacte-rial 16S rRNA gene universal primers as primers, PCR amplification could obtain a partial HY sequence with 1509bp and HG fragment with 1532bp. Based on the blasting of 16S rRNA gene sequence and phylogenetic tree, together with the physiologi-cal and biochemical characteristics analysis, HY and HG were identified as Aeromonas hydrophila and Vibrio parahaemolyti-cus, respectively. To our knowledge, this is the first report that A. hydrophila is a pathogen of S. serrata. Both HY and HG showed high sensitivity to Ofloxacin, Gentamicin, streptomycin and Amoxicillin, medium sensitivity to Sulfadiazine and Thiamphenicol, and no sensitivity to Benzylpenicillin Sodium. After the healthy mud crabs were infected with A. hydrophila by immersion or intramuscular injection and displayed typical symptoms, drug therapy shows 100% success rate after the infected crabs were bathed in Amoxicillin at 15μg/mL for three days.

Key words: Scylla serrata, Aeromonas hydrophila, Vibrio parahaemolyticus, histopathology, isolation and identification of pathogens, drug therapy