Prevalence of Flavobacterium psychrophilum Infection in Ayu (Plecoglossus altivelis) in Gunma Prefecture, Japan and Comparison of the gyr B Sequences of Isolates

บทคัดย่อ

The prevalence of cold-water disease (CWD) in ayu (Plecoglossus altivelis) caused by Flavobacterium psychrophilum was investigated in 3 different sites along the Tone River in Gunma Prefecture, Japan. F. psychrophilum was isolated from 7 of 8 fishes from site A (88%), 15 of 101 from site B (15%), and 3 of 8 from site C (38%). The gene encoding DNA gyrase subunit B (gyrB) of F. psychrophilum in 16 isolates was partially sequenced. Among the 16 strains, 15 strains had gene sequences that completely matched those of a species type strain (NCIMB1947^T). Another strain confirmed one nucleotide substitution, however, the codon resulting from this substitution was synonymous with that in the type strain sequence. The results suggested that CWD was widespread in the Tone River of Gunma Prefecture, with little genetic divergence from the species type strain.