Risk assessments of the emerging fish pathogen in the environmental condition of rising water temperature.

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TH-CR(Todd-Hewitt Congo red) agar was developed to detect and presumptively identify the GCSD(Group C Streptococcus dysgalactiae) obtained from artificially or naturally infected fish. Typical symptoms were observed in artificially infected fish at higher temperature(28°C), thus need an attention at the high water temperature season. The genetic analysis revealed that the fish isolates were genetically very similar to each other with high DNA. DNA relatedness and sequence homology. Seventeen isolates in GCSD collected Asian countries were found to be resistant to oxytetracycline and carried the tet(M) gene, except for the strains collected in Taiwan and the PP1564 strain collected in China. The amino acid sequence of SOF was identical among fish isolates. A primer set targeting the sof-FD gene was designed and applied to a PCR assay for discriminating fish isolates from mammalian isolates.