New mobile gene cassettes containing an aminoglycoside resistance gene, aacA7, and a chloramphenicol resistance gene, catB3, in an integron in pBWH301.

The multidrug resistance plasmid pBWH301 was shown to contain a sull-associated integron with five inserted gene cassettes, aacA7-catB3-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 cassettes. The aacA7 gene encodes a protein that is a member of one of the three known families of aminoglycoside acetyltransferases classified as AAC(6')-I. The chloramphenicol acetyltransferase encoded by the catB3 gene is closely related to members of a recently identified family of chloramphenicol acetyltransferases. The catB3 gene displays a relatively high degree of sequence identity to a chromosomally located open reading frame in Pseudomonas aeruginosa, and this may represent evidence for the acquisition by a cassette of a chromosomal gene.