Assessment of genetic variability and relatedness among atypical Aeromonas salmonicida from marine fishes, using AFLP-fingerprinting.
Atypical strains of Aeromonas salmonicida are the causal agent of atypical furunculosis or ulcer disease in various fish species, including spotted wolffish Anarhichas minor, which is a promising species in the Norwegian fish-farming industry. Isolates of atypical A. salmonicida comprise a very heterogenous group showing large variety in biochemical, molecular and virulence characteristics. The genetic variability among atypical isolates from wolffish was characterised using amplified fragment length polymorphism analysis: AFLP-fingerprinting. Additional isolates from halibut Hippoglossus hippoglossus, turbot Scophthalmus maximus, cod Gadus morhua and several salmonid fishes were included for assessment of variability and relatedness among a total of 56 atypical isolates of A. salmonicida. They were compared to reference strains of A. salmonicida subspecies and to other Aeromonas species pathogenic in fishes. AFLP-fingerprints subjected to similarity analysis yielded a grouping of the isolates into several clusters, revealing genetic heterogeneity among the isolates. There seems to be a correlation between genetic similarity among isolates and the fish host. The Icelandic isolates, mainly from cod, formed a very homogeneous subcluster, which was closely related to the wolffish isolates. All atypical isolates from spotted and common wolffish grouped together in a large cluster and appear to be very homogeneous, even though they had been isolated over a period of 8 yr at different locations in Norway. On the other hand, most of the isolates from turbot and halibut grouped together into 2 different clusters, while the 9 atypical isolates from salmonids appeared in 4 different clusters. Thus, the atypical isolates of A. salmonicida from halibut, turbot and salmonid fishes seem to be more genetically diverse than those from wolffish and cod.
Fiskeriforskning, Norwegian Institute of Fisheries and Aquaculture Ltd, Tromsø. vera.lund@fiskforsk.norut.no
Vera
V
Lund
Liss M
LM
Jenssen
Mette S
MS
Wesmajervi
D000333:Aeromonas / Q000235:genetics* / Q000302:isolation & purification; D000818:Animals; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000737:chemistry; D005393:Fish Diseases / Q000821:virology; D005399:Fishes; D005412:Flatfishes; D014644:Genetic Variation; D016905:Gram-Negative Bacterial Infections / Q000662:veterinary / Q000821:virology; D011110:Polymorphism, Genetic; D012487:Salmonidae
D004269:DNA, Bacterial