The transposon-like structure of IS26-tetracycline, and kanamycin resistance determinant derived from transferable R plasmid of fish pathogen, Pasteurella piscicida

Abstract

Tetracycline (pp-tet), and kanamycin (pp-kan) resistance genes were cloned from a transferable R plasmid of fish pathogen Pasteurella piscicida, and complete nucleotide sequences were determined. The pp-tet was a class D Tet determinant constructed with the tetA resistance gene of 1,182 bp encoding a protein with a deduced molecular mass of 41 kDa and the tetR repressor gene of 654 bp encoding a product of 24 kDa. The pp-tet was highly homologous to the tet(D) of plasmid RA1 isolated from Aeromonas hydrophila with two nucleotide differences in the tetR, and of plasmid pIP173 from Salmonella ordonez with two nucleotide differences in the tetA. The pp-kan contained 813 bp encoding a 31 kDa protein of 271 amino acids, and was classified into type aph-Ic. It was identical to the aphA7 in the IAB operon of pBWH77, in which was originally found an isolate of Klebsiella pneumoniae, in its nucleotide sequences and hybrid promoter construction. The genes were connected by an insertion sequence IS26 of 820 bp, and were flanked by repeated copies in direct orientation at the 3' flanking region of the pp-tetA and in inverted orientation at the 3' flanking region of the pp-kan. The genetic elements are organized like a complex transposon by close linkage of the IS26 and the pp-tet and -kan.