To further characterize Tn5431, which is composed of Tn3 and Tn1721, D
NA sequencing was carried out. It was demonstrated that Tn5431 arose b
y transposition of Tn3 into Tn1721. Multiple mutations in the Tn3 tnpA
gene have occurred, rendering the Tn3 portion of Tn5431 transposition
defective and ensuring the simultaneous transposition of the antibiot
ic resistance determinants on Tn3 and Tn1721.