Sulfonamide resistance gene in a transferable R plasmid of Pasteurella piscicida

The sulfonamide resistance (SAr) determinant was cloned from a transferable R plasmid of Pasteurella piscicida, pSP9351, and the sequence was determined. The resistance gene (pp-sul) was localized to an approximately 1-kb region that includes the PstI-EcoRI site in the restriction map. An open reading frame coding a sul II-type gene composed of 810 nucleotides was identified. A direct repeat sequence was shown in the 5' flanking region of pp-sul, and a plasmid recombinational event may have occurred during the construction of pSP9351. In the 3' flanking region of the gene, a sequence homologous to the 5' noncoding sequence of the trimethoprim resistance gene, dhfr IX was found.