NEW MOBILE GENE CASSETTES CONTAINING AN AMINOGLYCOSIDE RESISTANCE GENE, AACA7, AND A CHLORAMPHENICOL RESISTANCE GENE, CATB3, IN AN INTEGRONIN PBWH301

The multidrug resistance plasmid pBWH301 was shown to contain a sull-a ssociated integron with five inserted gene cassettes, aacA7-cafB3-aadB -oxa2-orfD, all of which can be mobilized by the integron-encoded DNA integrase. The aadB, oxa2, and orfD cassettes are identical to known c assettes. The aacA7 gene encodes a protein that is a member of one of the three known families of aminoglycoside acetyltransferases classifi ed as AAC(6')-I. The chloramphenicol acetyltransferase encoded by the catB3 gene is closely related to members of a recently identified fami ly of chloramphenicol acetyltransferases. The catB3 gene displays a re latively high degree of sequence identity to a chromosomally located o pen reading frame in Pseudomonas aeruginosa, and this may represent ev idence for the acquisition by a cassette of a chromosomal gene.