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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Aquatic Animal Health Strategies

Location: Aquatic Animal Health Research

Title: Phenotypic and genetic characterization of bacteria isolated from diseased cultured sea cucumber (Apostichopus japonicus) in Northeastern China

Authors
item Li, Hua -
item Qiao, Guo -
item Gu, Jie Quan -
item Zhou, Wei -
item Li, Qiang -
item Woo, S-H -
item Xu, Dehai
item Park, S-I -

Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 21, 2010
Publication Date: September 17, 2010
Repository URL: http://handle.nal.usda.gov/10113/55871
Citation: Li, H., Qiao, G., Gu, J., Zhou, W., Li, Q., Woo, S., Xu, D., Park, S. 2010. Phenotypic and genetic characterization of bacteria isolated from diseased cultured sea cucumber (Apostichopus japonicus) in Northeastern China. Diseases of Aquatic Organisms. 91:223-235.

Interpretive Summary: Sea cucumber (Apostichopus japonicus ) has become a prominent aquaculture species in many Asian countries. Diseases cause 20-40% mortality of cultured sea cucumbers and lead to heavy economic losses in sea cucumber culture. No information is available for the distribution, diversity and appearance of pathogens in sea cucumber cultured area. The objective of this study is to carry out a precise characterization of bacterial pathogens responsible for outbreaks that affected the cultured sea cucumber during the winter-spring from 2004 to 2006 in Northeastern China. The results showed that clinical signs of diseased sea cucumber included swollen mouth, skin ulceration and massive mortality. Thirty-one bacterial samples were isolated from diseased sea cucumbers taken during this period and identified through biochemical tests, gene sequence analysis and PCR amplification, followed by pathogenicity determination. The results showed that the 31 isolates belonged to the genera Vibrio (64.5%), Shewanella (12.9%), Serratia (12.9%), Pseudoalteromonas (6.4%) and Flavobacterium (3.2%). The 3 prominent strains were Vibrio splendidus (41.9%), Shewanella (12.9%) and Serratia odorifera biogroup I (12.9%). Pathogenicity tests demonstrated that 13 out of 31 isolates were pathogenic, including 8 strains of V. splendidus, 3 strains of Shewanella sp. and 2 strains of Pseudoalteromonas tetraodonis. The results in this study help to understand the pathogenic mechanisms of bacteria, predict outbreaks of bacterial diseases in sea cucumbers and enhance management to reduce the loss of cultured sea cucumbers due to the diseases.

Technical Abstract: During the winter–spring from 2004 to 2006 in northeastern China cultured Japanese sea cucumber Apostichopus japonicus suffered from a serious disease. Clinical signs included swollen mouth, skin ulceration and massive mortality. Clinical samples taken during this period were studied. Thirty-one bacterial samples were isolated from diseased sea cucumbers and identified through biochemical tests, 16S rRNA gene sequence analysis and PCR amplification, followed by pathogenicity determination. The results showed that the 31 isolates belonged to the genera Vibrio (64.5%), Shewanella (12.9%), Serratia (12.9%), Pseudoalteromonas (6.4%) and Flavobacterium (3.2%). The 3 prominent strains were Vibrio splendidus (41.9%), Shewanella (12.9%) and Serratia odorifera biogroup I (12.9%). Pathogenicity tests demonstrated that 13 out of 31 isolates were pathogenic, including 8 strains of V. splendidus, 3 strains of Shewanella sp. and 2 strains of Pseudoalteromonas tetraodonis. The pathogenic V. splendidus showed the highest frequency of appearance. Median lethal dose (LD50) values (14 d) of V. splendidus, Shewanella sp. and P. tetraodonis were 1.74 × 107, 7.76 × 106, 7.24 × 107 CFU g–1 body weight of sea cucumber, respectively. The virulences differed by species: Shewanella sp. > V. splendidus > P. tetraodonis. This is the first report of Shewanella sp. virulence in sea cucumber.

Last Modified: 9/1/2014
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