3). All the Taiwanese strains (except 95985 and AOD-96086-K) and the Chinese strains PP1564 and PP1635 showed an identical genotype (D). All the Japanese isolates were grouped into genotypes A, B, and C, while the genotype of the Malaysian strain WSSN1609 was B. On the other hand, the AOD-96086-K (E), 95985 (F), PP1398 (G), and PF880 (H) strains and the tilapia strain of T11358 (I) had unique profiles. This paper presents the first epidemiological KPT 330 comparison study comprising

a total of 30 strains of S. dysgalactiae isolated from diseased fish species in different Asian countries. The epidemiological study was conducted based on phenotypic characterization in addition to both sequencing of the sodA gene and BSFGE due to their high discriminative power. Most of the studies on the phenotypic characterization of streptococci, which have been reported thus far, used the API 20 STREP® and API ZYM® systems (Tillotson, 1982; Gruner et al., 1992). The biochemical

R428 mouse and enzymatic characterizations performed in this study revealed that all the fish isolates exhibited a high phenotypic homogeneity irrespective of their country of origin as well as the fish species, and their comparison with the reference strain ATCC43078 revealed that all tested fish isolates could hydrolyze arginine, but could not acidify lactose. Therefore, the phenotypic homogeneity should be taken into account when these systems are used for routine identification of clinical isolates of S. dysgalactiae. All the isolates carried the tet(M) gene, except for the Taiwanese isolates and the PP1564 isolate collected Y-27632 in China, resulting in resistance to oxytetracycline. This finding suggested that the oxytetracycline-resistance gene

tet(M) prevailed in the majority of fish S. dysgalactiae isolates collected in various Asian countries. This fact concurred with the results obtained by Kim et al. (2004), who suggested that the tet(M) gene was present in fish intestinal and seawater bacteria at aquaculture sites, and these bacteria could be important reservoirs of tetracycline-resistance genes in the marine environment. The sequencing of the sodA gene was performed for the genetic comparison characterization between Japanese fish and mammalian isolates of S. dysgalactiae (Nomoto et al., 2008). In this study, sequencing of the sodA gene was performed in order to compare different fish isolates collected from various Asian countries. As a result, a 100% sequence identity was observed among the fish isolates irrespective of their country of origin, except for KNH07902, in which a single nucleotide differed from that of the other isolates. This finding revealed the homogeneity among fish isolates irrespective of the country of origin as well as the fish species.