Streptococcus dysgalactiae is an emerging pathogen of fish. Clinically, infection is characterized by
the development of necrotic lesions at the caudal peduncle of infected fishes. The pathogen has
been recently isolated from different fish species in many countries. Twenty S. dysgalactiae isolates
collected from Japan, Taiwan, Malaysia and Indonesia were molecularly characterized by biased
sinusoidal field gel electrophoresis (BSFGE) using SmaI enzyme, and tuf gene sequencing analysis.
DNA sequencing of ten S. dysgalactiae revealed no genetic variation in the tuf amplicons, except
for three strains. The restriction patterns of chromosomal DNA measured by BSFGE were differentiated
into six distinct types and one subtype among collected strains. To our knowledge, this
report gives the first snapshot of S. dysgalactiae isolates collected from different countries that
are localized geographically and differed on a multinational level. This genetic unrelatedness
among different isolates might suggest a high recombination rate and low genetic stability.