Characterisation by restriction endonuclease analysis and plasmid profiling of Vibrio ordalii strains from salmon (oncorhynchus tshawytscha and oncorhynchus nerka) with vibriosis in new zealand

Isolates of Vibrio ordalii were recovered from salmon (Oncorhynchus tshawytscha and Oncorhynchus nerka) cultured in New Zealand. The fish suffered from clinical vibriosis, from seven outbreaks in five geographically distinct areas. Affected fish showed gross signs and histopathology similar to those reported from North America. The presence of a plasmid, designated pVO1, approximately 30 kilobases (kb) in size, was seen in all V. ordalii strains examined This plasmid was identical in size and restriction endonuclease cleavage analysis to a plasmid (pMJ101) previously found in V. ordalii strains elsewhere. After togging pVO1 with the transposon Tn1 from the R plasmid RP4, attempts to isolate plasmid-less derivatives using a variety of curing agents were unsuccessful. All of the New Zealand isolates possessed identical chromosomal DNA cleavage patterns. These patterns were only slightly different from that of the type strain but substantially different from that of the Vibrio anguillarum type strain.