SEQUENCING AND EXPRESSION OF AADA, BLA, AND TNPR FROM THE MULTIRESISTANCE TRANSPOSON TN1331

A fragment of Tn1331 includingtnpR, aac, aadA,and abla gene which encodes lower levels of resistance to ampicillin and carbenicillin as compared to those mediated by the TEM β-lactamase was sequenced. The polypeptide encoded by thebla gene has homology with the OXA-1, PSE-2, and OXA-2 proteins. Genesaac and bla are upstream and downstream respectively ofaadA, and are both flanked by recombinational hot spots. Tn1331 has 520-bp direct repeats which include parts of thetnpR and TEMbla genes. Evolutionary models for the genesis of Tn1331 are proposed. © 1990 Academic Press, Inc. All rights reserved.