The objective of this study was to develop a real-time PCR method for the rapid detection and quantification of the protozoan pathogen Perkinsus olseni using a TaqMan probe. For the standard, genomic DNA was extracted from 10 5 in vitro-cultured P. olseni trophozoites, and then 10-fold serial dilutions to the level of a single cell were prepared. To test the reliability of the technique, triplicates of genomic DNA were extracted from 5 × 10 4 cells and 10-fold serial dilutions to the level of 5

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... cells were prepared. The standards and samples were analyzed in duplicate using an Exicycler TM 96 real-time quantitative thermal block. For quantification, the threshold cycle (CT) values of samples were compared with those obtained from standard dilutions. There was a strong linear relationship between the CT value and the log concentration of cells in the standard (r 2 = 0.996). Detection of DNA at a concentration as low as the equivalent of a single cell showed that the assay was sensitive enough to detect a single cell of P. olseni. The estimated number of P. olseni cells was similar to the original cell concentrations, indicating the reliability of P. olseni quantification by real-time PCR. Accordingly, the designed primers and probe may be used for the rapid detection and quantification of P. olseni from clam tissue, environmental water, and sediment samples.