Genetic stability and worldwide dissemination of integron insert encoding trimethoprim resistance.

A hospital-based surveillance study of class 1 integron-positive Acinetobacter isolates in the Urals and Siberia (Russia) demonstrated that dihydrofolate reductase gene (dfrA5) was located in a functional gene cassette insertion driven from a promoter of a weak type. This insertion is an example of the integron-associated trimethoprim resistance disseminated worldwide from the free-living animals to human. Despite the long-term persistence as an integron insert any loss or modifications in the nucleotide sequence especially at attC site was not observed. Nucleotide sequence previously referred as a weak type promoter may be considered as a wild-type configuration of an integron promoter region.