title: Genetic characteristics of Streptococcus dysgalactiae isolated from cage cultured cobia, Rachycentron canadum (L.).
abstract: Disease outbreaks occurred during 2007-2013 in Taiwan with 2.5-10% mortality among the cage cultured cobia, Rachycentron canadum (L.), characterized by the presence of polyserositis, pericarditis and peritonitis. The micro-organisms isolated from internal organs were Gram-positive cocci. The isolates were confirmed as Streptococcus dysgalactiae by a polymerase chain reaction assay that yielded the expected specific 259 bp amplicon. Additionally, partial sequence of the 16S-23S rDNA intergenic spacer region of the GCS strain isolates from fish was also compared and produced 100% sequence identity with S. dysgalactiae (GenBank accession number AB252398). The genetic characterization was then determined by pulsed-field gel electrophoresis (PFGE) analysis. Based on PFGE, the Apa I or Sma I digestion patterns of chromosomal DNA of these isolates were grouped into three main clusters. Taiwanese strains were divided into two clusters, and the tet(M) gene was detected in cluster 1 (pulsotypes: A1-A2 and S1-S3), but not in cluster 2 strains (pulsotypes: A3-A4 and S4-S5). Three Japanese strains from amberjack, Seriola dumerili (Risso), were grouped into cluster 3 (pulsotypes: A5-A7 and S6-S8) and displayed no mortality to cobia in the challenge experiment. Conversely, Taiwanese strains from cobia and snubnose pompano, Trachinotus blochii (L.), displayed a mortality rate of 50-87.5% in cobia.
authors.affiliation: Department of Veterinary Medicine, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwan.
authors.forename: M-A
authors.initials: MA
authors.lastname: Tsai
authors.affiliation: Department of Veterinary Medicine, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwan.
authors.forename: P-C
authors.initials: PC
authors.lastname: Wang
authors.affiliation: Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, Miyazaki University, Miyazaki, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Department of Veterinary Medicine, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwan.
authors.forename: S-C
authors.initials: SC
authors.lastname: Chen
mesh_terms: D000818:Animals; D001483:Base Sequence; D021901:DNA, Intergenic / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D005393:Fish Diseases / Q000382:microbiology* / Q000473:pathology; D005398:Fisheries; D008969:Molecular Sequence Data; D010473:Perciformes / Q000382:microbiology*; D010493:Pericarditis / Q000382:microbiology / Q000473:pathology / Q000662:veterinary; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000662:veterinary; D013290:Streptococcal Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D013291:Streptococcus / Q000235:genetics* / Q000302:isolation & purification; D013753:Tetracycline Resistance / Q000235:genetics
chemical_list: D021901:DNA, Intergenic
keywords: 16S-23S rDNA intergenic spacer gene; Streptococcus dysgalactiae; cobia; pulsed-field gel electrophoresis