| BackgroundsThe serious abuse of antibiotics has promoted the rapid development of bacteria resistance. At present, bacteria resistance has gradually become a severe and universal problem, leading to the ineffective clinical treatment of antimicrobial agents. It has been associated with the higher cost of clinical treatment and shorter period of new drugs application, and threatenes the health of human directly. In traditional concepts, bacteria resistance is caused by gene mutation, however, it has no transmissibility. In recent years, integrons which consists of 5' conserved segment, 3' conserved segment and a variable region between the two conserved segments, have been found to be a novel mobilizable element concerned with gene capture and expression. By integrase, integron can capture external drug-resistance genes which are expressed by the promoter located upstream of integron, so that bacteria containing integron have resistance and multidrug resistance. Integron can excise the genes in its variable region as free circle molecules, and mediate the transmissibility of bacteria resistance. It has been an important reason for the rapid spread of resistance in bacteria, especially in gram negative bacteia. However, the frequency, characteristics, and roles of integrons and gene cassettes have not yet been investigated in a large-scale population of bacteria.
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