魚病原細菌Photobacterium damselae subsp. piscicidaの伝達性Ｒプラスミドのクロラムフェニコールおよび エリスロマイシン耐性因子のクローニングと塩基配列解析

Transferable resistance to various drugs was investigated in a strain of Photobacterium damselae subsp. piscicida from Japan. Drug resistance was transferred via three plasmids of 100, 50, and 40 kirobases (kb). Resistances to choloramphenicol and erythromycin were transferred on the 40-kb plasmid pPDP9106b. The cloned PstⅠ fragment of pPDP9106b was determined as being 6377 base pairs (bp). The chloramphenicol resistance gene conferring cross-resistance to florfenicol has been designated floR, which was found to be part of the 4279-bp transposon and coded 404 amino acid residues with a calculated molecular mass of 42.6 kDa. The transposon consisted of the gene floR, a putative regulatory gene (101 amino acid residues), and the transposase gene tnpA (497 amino acid residues) and constituted a circular form. The erythromycin resistance gene designated as ermM, which coded 303 amino acid residues with a calculated molecular mass of 35.6 kDa, was suggested to be a novel 23S rRNA methyltransferase from the presence of nine conserved sequence motifs that are important in target sequence, catalysis, and S-adenosyl-L-methionine binding and very low homology (35 to 15%) between the ErmM protein of P.damselae and the 23S rRNA methyltransferases of nineteen other bacteria