Circularized copies of amplifiable resistance genes from Haemophilus influenzae plasmids.

Tandem repeat amplification of resistance determinants in Haemophilus influenzae plasmids is associated with the occurrence of separate circular DNA molecules. They were demonstrated to represent mono- and multimeric forms of the amplifiable segments of the plasmids which comprise the respective resistance transposons and an additional region designated as an amplification sequence. The latter region mediates the recombinational events involved in amplification. The DNA circles apparently lack the ability to replicate autonomously but most probably provide an effective means for the translocation of resistance genes from one plasmid to another.