The Structure of the Chloramphenicol Resistance Gene on a Transferable R Plasmid from the Fish Pathogen, Pasteurella piscicida

Abstract

The chloramphenicol resistance gene (pp‐cat) was cloned from a transferable R plasmid of Pasteurella piscicida, pSP9351, and the sequence of the gene was determined. Subcloning and deletion analysis localized the resistance gene, pp‐cat, to within a 2.3 kb HincII‐BamHI fragment. The fragment as a probe hybridized with the type I chloramphenicol acetyltransferase (CAT) gene and did not hybridize to CAT types II, III, and CAT‐VA. The fragment hybridized to transferable R plasmids encoded with resistance to chloramphenicol, which were detected from P. piscicida isolated in different years. Nucleotide sequences of the coding and flanking regions of pp‐cat (2031 bp) identified an open reading frame coding type I CAT of a molecular mass of about 25,000 Da. Comparison analysis of the sequences outside the cat open reading frame showed also that pp‐cat has homology, in part, with the gene that coding for the endonuclease EcoRII and those that flank the cat gene derived from the Acinetobacter baumannii chromosome.