Title: Quantitative detection of the spoilage bacteria Pseudomonas spp. and Photobacterium phosphoreum in fish by real-time PCR

The Pseudomonas spp and Photobacterium phosphoreum have been found as the specific spoilage organisms of fish. The aim of this study was to develop rapid and accurate quantitative assay for Pseudomonas spp. and Photobacterium phosphoreum in redfish and Salmon fillets using real-time PCR. Because the redfish material is not free from P. phosphoreum and P. fluorescens, only real-time PCR assay for Pseudomonas spp. and Photobacterium phosphoreum in salmon fillets was established. Results indicated that the real-time was most effective when the AB Teq polymerase mixture and DNA extracted by MasterPure™ DNA Purification Kit were used. Real-time PCR using DNA extracted by MasterPure™ DNA Purification Kit was able to determine the Log10 number CFU/g of P. phosphoreum in salmon fillets matrix from 3.22 to 7.40 in nature salmon fillet. The detection time of this method was only 5 h. Real-time PCR using DNA prepared by MasterPure™ DNA Purification Kit could provide the Log number of Pseudomonas spp. in salmon matrix from 2.19 to 6.30 directly. The detection time of this method was only 5 h. In conclusion, the real-time PCR was a quick method to quantity the P. phosphoreum and Pseudomonas spp. in salmon fish.