Establishemnt of a specific PCR assay to detect Nocardia seriolae

Nocardia seriolae, one of the main pathogenic bacterium of cultured largemouth bass Micropterus salmoides in South China, grows very slowly in culture medium, so it is difficult for its isolation and identification. In present study, two specific primers were designed according to the genomic sequence of 16S~23S intergenic spacers (ITS) to establish a rapid specific PCR assay to detect N.seriolae. Results indicate that the 2 primers are very specific to detect N.seriolae and show positive to very little of DNA amount at 5 pg. In addition, a rapid PCR detection kit was developed which was then applied to detect the N.seriolae-infected tissues of M.salmoides. The PCR kit can detect positive fragments from M.salmoides without any obvious disease symptoms, so it is superior to traditional method in terms of sensitivity and efficiency, having good potential in clinical diagnose in aquaculture.