Abstract
A new trimethoprim resistance determinant, designated dhfrX, was identified in the In7 integron of pDGO100. The sequence of the dhfrX dihydrofolate reductase is up to 28% identical to the sequences of several known dihydrofolate reductase proteins. The dhfrX gene is adjacent to the second 3'-conserved segment of the In7 integron, but the first 77 bases of this segment are not present.