Biocide use, integrons and novel genetic elements

Resistance to antibiotics threatens our ability to control bacterial pathogens. It is clear that the persistence of cells containing resistance determinants is promoted by the strong selective pressure imposed by antibiotic use. This problem has been exacerbated by inappropriate and excessive use of antibiotics in both medicine and animal production. Concern has also been raised that inappropriate use of biocides contributes to the selection of resistant bacterial strains. This may occur because detoxification mechanisms for biocides and antibiotics are shared, or via selection for biocide resistance genes that are physically linked to antibiotic resistance genes and their mobile DNA vectors. In this brief review I will illustrate the latter phenomenon using the evolutionary history of the class 1 integron as an example, and then examine whether the increasing trend towards indiscriminate use of biocides in homes and consumer products might result in the selection of novel genetic elements that will have negative and unpredictable consequences for human health.