The development of antibiotic resistant strains of bacteria that are problematic and expensive to treat is a major healthcare problem around the world. The "selective pressure" of antibiotic usage inevitably results in the emergence and proliferation of resistant bacteria.
Strains commonly become resistant by acquiring a pre-existing resistance gene from other bacteria. This is possible because resistance genes are often carried on "mobile" DNA molecules called plasmids, which are "mini-chromosomes" that can be transmitted from resistant bacteria to sensitive ones, rapidly making them resistant in the process.
The ability to share genes makes bacteria masters of adaptation; bacterial populations can rapidly become resistant when exposed to an antibiotic. In contrast, once a resistance gene is acquired it is usually lost very slowly, if at all, even when the antibiotic is no longer used, because plasmids are inherited very efficiently. This persistence of plasmids exacerbates the situation because as the bacteria are subsequently exposed to different types of antibiotics they accumulate resistance genes and become increasingly multiply resistant, leaving fewer and fewer effective treatments.
Currently, there are few options to limit the evolution of resistant bacteria, other than to minimize the unnecessary use of antibiotics. A research team, which includes Professor Ron Skurray and Dr Neville Firth from the School of Biological Sciences at the University of Sydney and Dr Maria Schumacher from the University of Texas MD Anderson Cancer Centre, is working on new ways to combat resistance.