African Journal of
Microbiology Research

  • Abbreviation: Afr. J. Microbiol. Res.
  • Language: English
  • ISSN: 1996-0808
  • DOI: 10.5897/AJMR
  • Start Year: 2007
  • Published Articles: 5232

Full Length Research Paper

Isolation and characterization of Streptococcus agalactiae from Nile Tilapia Oreochromis niloticus in China

Kai-yu Wang1,2*#, De-fang Chen1,3#, Ling-yuan Huang1#, Hai Lian1, Jun Wang1, Dan Xiao4, Yi Geng2, Ze-xiao Yang2 and Wei-ming Lai1
1Research Center of Fish Disease, Sichuan Agricultural University, Ya’an, Sichuan 625014, People’s Republic of China. 2Key Laboratory of Animal Disease and Human Health of Sichuan Province, Sichuan Agricultural University, Ya’an, Sichuan 625014, People’s Republic of China. 3Department of Aquaculture, Sichuan Agricultural University, Ya’an, Sichuan 625014, People’s Republic of China. 4Animal Health Research Institute of Tongwei Co., Ltd., Chengdu, Sichuan 610041, People’s Republic of China
Email: [email protected]

  •  Accepted: 24 January 2013
  •  Published: 31 January 2013

Abstract

Streptococcosis became an increasingly significant health problem in intensive aquaculture in China. In 2009, eight Gram-positive, chain-forming coccus strains were isolated from the outbreak epidemical diseased tilapias from Hainan Province, China. Characteristics based on morphological, physiological and biochemical tests show that the eight strains were suggested to Streptococcus agalactiae. Furthermore, sequencing of the 16S rRNA genes shows high sequence similarities (99.5 to 99.9%) with S. agalactiae. All results indicated that the eight isolated strains (Genbank no JF423941~JF423948) were S. agalactiae. The median lethal doses (LD50) of HN0101 and HN0301 which were isolated from Wenchang and Xinglong villages were 6.8×10and 5.3×10CFU/fish, respectively by intraperitoneal injections. All the isolates were sensitive to cefoxitin, and had quite different sensitiveness to other antibiotics. This research hinted that S. agalactiae had become an important potential bacterial agent of tilapias in the south of China.

 

Key words: Streptococcus agalactiae, tilapia, identification