Application of AFLP for taxonomic and epidemiological studies of Photobacterium damselae subsp piscicida

A collection of 106 Photobacterium damselae subsp. piscicida strains and 19 Photobacterium damselae subsp. damselae strains, including reference and t ype strains, were genetically characterized using AFLP. The total genomic D NA of each bacterial strain was digested using restriction endonucleases Hi ndIII and TaqI. Using numerical analysis, six clusters were recognized. The largest cluster (n = 106) contained the majority of the strains tested and consisted exclusively of Photobacterium damselae subsp. piscicida. The Pho tobacterium damselae subsp. damselae strains fell outside this cluster. DNA -DNA hybridization experiments showed 77% DNA binding between the two subsp ecies, indicating a close genetic relationship. This clearly demonstrates t he applicability of AFLP in studying the taxonomic position of Photobacteri um damselae subsp. piscicida. In addition, AFLP proved to be a useful genot ypic technique for epidemiological surveys of the pathogen, since it was ab le to discriminate between Mediterranean and Japanese Photobacterium damsel ae subsp. piscicida isolates.