Integron and antibiotic resistance

Abstract

Since the advent of antibiotic chemotherapy, the spread of drug resistance genes among clinical isolates of bacteria has become an ever-increasing problem. The increase in drug resistance has been facilitated by the association of antibiotic resistance genes with a variety of mobile genetic elements including plasmids, transposons, integrons and gene cassettes. How then have plasmids and transposons acquired such a vast array of genes in the last 50 years? In Gram-negative bacteria (GNB) this can be explained, in part, by the presence of integrons, since these elements can efficiently capture mobile gene cassettes and their associated antibiotic resistance genes, thereby transferring resistance from one bacterium to the next. Many of the antibiotic resistance genes found in clinical isolates of Gram-negative bacilli are part of a gene cassette inserted into an integron, and the sequences of over 100 cassettes are known. Integrons are found within the context of a number of fundamentally different plasmids and transposons, which suggests that they are mobile elements. An integron is any genetic unit that contains the determinants of a site-specific recombination system capable of capturing and mobilising genes that are contained in gene cassettes. This study describes the prevalence of integrons in clinical isolates from Australia and the impact they have on antibiotic resistance.