The Thai Journal of Veterinary Medicine


Warm-water streptococcosis outbreaks in Thai cultured tilapia are caused by Streptococcus iniae and S.agalactiae. However, distinguishing between these two species of streptococcus are very difficult due to their similarmicrobiological appearance and clinical signs of infected fish. In this study, we proposed a new duplex-PCR basedmethod for simultaneous detection of these pathogens. The duplex-PCR amplified partial lctO and 16s rRNA gene ofS. iniae and S. agalactiae at 870 bp and 220 bp, respectively. This technique gave 100% specificity while sensitivity ofreaction was 100 fg of each bacterial genomic DNA. Detection limit of duplex-PCR applicable to clinical specimens isalso evaluated as 106 bacterial cells per gram of fish tissue. This study suggested that this duplex-PCR based methodmight be a good candidate for easy, sensitive, specific and rapid detection of S. iniae and S. agalactiae associated withwarm-water streptococcosis of cultured tilapia in Thailand.

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