Restriction endonuclease analysis of atypical Aeromonas salmonicida isolates from goldfish Carassius auratus, silver perch Bidyanus bidyanus, and greenback flounder Rhombosolea tapirina in Australia

Total genomic DNA samples of atypical isolates of Aeromonas salmonicida from goldfish Carassius auratus L., silver perch Bidyanus bidyanus (Mitchell), and greenback flounder Rhombosolea tapirina Giinther from Australia and isolates from goldfish from the USA and Singapore were digested with the restriction enzyme Cfol, separated In 3.5% acrylamide gels and visualised by silver staining. Isolates from goldfish and silver perch comprised an homogenous group while those from greenback flounder formed a second group. Within the goldfish and silver perch isolates there were minor differences in restriction endonuclease fragment pattern. Isolates from Australian goldfish obtained between 1977 and 1989 were indistinguishable from isolates from goldfish from the USA but slightly different from an isolate from a Singaporean goldfish. These and other data suggest that A. salmonicidaprobably crossed a species barrier from goldfish to silver perch on the same farm but that farmed greenback flounder In Tasmania have acquired a distinct straln of A. saln~onicida probably from wild-caught marine fish.