Simple and rapid detection of Photobacterium damselae ssp. piscicida by a PCR technique and plating method

AIMS: To detect Photobacterium damselae ssp. piscicida using the PCR technique and plating method. METHODS AND RESULTS: Two strains of P. damselae ssp. piscicida were isolated from cultured cobia (Rachycentron canadum) at two different fish farms in Taiwan. A pair of primers was designed to detect the capsular polysaccharide gene of P. damselae ssp. piscicida by PCR. Reference strains of different genus and different clinical strains were used for this study. The expected product (410 bp) was obtained from both P. damselae ssp. piscicida and P. damselae ssp. damselae, and they were differentiated by culturing on thiosulphate citrate bile salts-sucrose agar (TCBS-1). Photobacterium damselae ssp. damselae grew on TCBS-1 producing green colonies whereas P. damselae ssp. piscicida did not grow. CONCLUSIONS: The methods used are cost and labour effective when compared with the other methods and commercially available kits. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides an integrated set of methods to identify the species P. damselae and to differentiate P. damselae ssp. piscicida from P. damselae ssp. damselae.