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Diseases of Aquatic Organisms

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DAO 119:207-217 (2016)  -  DOI:

Characterization and identification of streptococci from golden pompano in China

X. H. Cai1,2, Y. H. Peng2, Z. C. Wang2, T. Huang3, X. Y. Xiong2, Y. C. Huang1, B. Wang1, L. W. Xu4, Z. H. Wu1,* 

1Guangdong Provincial Key Laboratory of Pathogenic Biology and Epidemiology for Aquatic Economic Animals, Guangdong Key Laboratory of Control for Diseases of Aquatic Economic Animals, Guangdong Ocean University, Zhanjiang 524088, PR China
2Guangxi Key Laboratory of Marine Biotechnology, Guangxi Institute of Oceanology, Beihai 536000, PR China
3Guangxi Key Laboratory of Aquatic Genetic Breeding and Healthy Aquaculture, Guangxi Academy of Fishery Sciences, Guangxi 530021, PR China
4South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou 510300, PR China
*Corresponding author:

ABSTRACT: Streptococcal infections cause significant mortality and high economic losses in the fish farm industry worldwide, including in the culture of golden pompano Trachinotus ovatus L., a species gaining popularity in China. A total of 9 streptococcal strains were isolated from cage-cultured diseased golden pompano in Beihai, Zhanjing, and Shenzhen, China, between 2012 and 2014. Conventional and rapid identification systems were used to determine that the isolates were Streptococcus agalactiae, S. iniae, and S. dysgalactiae subsp. dysgalactiae. All isolates were gram-positive cocci cells in pairs or short-chain, non-motile, catalase negative, α or β hemolytic cocci. The results of multiplex PCR assays and 16S rRNA BLAST analysis also showed that the β hemolytic strains were S. agalactiae and S. iniae and the α hemolytic strain was S. dysgalactiae subsp. dysgalactiae, respectively. Pathogenicity assays revealed that S. agalactiae (lethal dose [LD50]: 6.38 × 104 CFU ml-1) was more virulent for golden pompano than S. iniae (LD50: 1.47 × 107 CFU ml-1) and S. dysgalactiae subsp. dysgalactiae (LD50: 2.57 × 106 CFU ml-1) when they were challenged by intraperiotoneal (i.p.) injection. The results of antibiotic susceptibility showed that all strains were extremely susceptible to cefradine, erythromycin, and cefotaxime but resistant to gentamicin, penicillin G, novobiocin, neomycin, ciprofloxacin, roxithromycin, furazolidone, enrofloxacin, norfloxacin, kanamycin, ampicillin, tetracycline, and vancomycin This is the first report of a phenomenon of golden pompano coinfection with S. agalactiae and S. iniae, which will contribute to the diagnosis and prevention of streptococcicosis.

KEY WORDS: Trachinotus ovatus · Streptococcus · Pathogenicity · Biochemical characterization · Multiplex PCR assay

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Cite this article as: Cai XH, Peng YH, Wang ZC, Huang T and others (2016) Characterization and identification of streptococci from golden pompano in China. Dis Aquat Org 119:207-217.

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