USE OF PCR TO DETECT CYTOPHAGA-PSYCHROPHILA FROM APPARENTLY HEALTHY JUVENILE AYU AND COHO SALMON EGGS

The nested PCR was used to detect Cytophaga psychrophila carried by ju venile ayu (Plecoglossus altivelis) and eyed eggs of coho salmon (Onco rhynchus kistch). Ayu juveniles were caught in Lake Biwa and frozen sh ortly after landed. The coho salmon eggs from the USA and Japan were c ollected on a lot-by-lot basis at Narita airport or hatcheries when th e containers arrived. Chelex 100 was used as a medium for extraction o f DNA from these samples. Utilizing the PCR, a specific primer pair of PSY1 and PSY2 for C. psychrophila was used to amplify its 16S rDNA se gments. An amplification product of the expected size was obtained fro m 5 of 24 DNA extractions from the kidney of ayu samples in April 1995 . These fish had been previously diagnosed as negative for the presenc e of C. psychrophila by cultivation on TYE agar and IFAT. Five of 11 l ots of coho salmon eggs were found to be positive for C. psychrophila by PCR. Four of these five lots had also been diagnosed as positive by cultivation and IFAT. In addition, the sensitivity of the PCR amplifi cation for detecting C. psychrophila in kidney samples of ayu was calc ulated to be 1.5 CFU per PCR reaction tube.