Abstract:Turbot Scophthalmus maximus was introduced into China in 1992. Since then, it has become one of the most dominant mariculture industries. In recent years, however, a main bottleneck constraining its commercial development is the disease problem prevailing in the farms and causing significant mortalities. Ascites syndrome is a disease that is commonly found in larvae culture and grow-out period. The present study investigated the diversity and antimicrobial resistance of the pathogens isolated from bacterial ascetic disease in cultured turbot S. maximus in Shandong Province. In total, 27 bacterial pathogens were collected from different regions of the province between 2002 and 2010. These 27 strains of pathogens were identified through the use of 16S rDNA gene sequence analysis and their antibiotic resistance profiles were tested with 22 common antibiotics using the Kirby-Bauer disc diffusion methodology. The antimicrobial susceptibility data were used to identify correlations between antibiogram and the change of resistance. The results demonstrated that V. scophthalmi, E. tarda, V. anguillarum, V. harveyi, P. espejiana were the pathogenic strains associated with ascetic disease of cultured turbot. The major pathogenic strain was V. scophthalmi in Qingdao area and E. tarda in Weihai area, whereas all pathogenic strains were equally found in Yantai area. Five bacterial strains were resistant to Penicillin, Cephalosporins, Macrolides and T/S with resistance rates over 50%. In addition, the resistance rate to FFC was below 10%, and was little drug resistance in the long-term use, suggesting that FFC is a favorable antibacterial drug to prevent and treat the ascites disease in cultured turbot. Twenty-seven pathogenic bacteria formed 27 antibiogram types since all the strains had multiple antibiotic resistance. 74.1% of the strains were resistant to more than ten different types of antibiotics. In conclusion, the drug resistance rates among aquatic bacteria were very high, becoming the primary problem in the prevention of aquatic bacterial diseases. The results provide theoretical basis and reference for the epidemiological studies of turbot ascetic disease and its early prevention.
