ABSTRACT
The use, overuse and misuse of antibiotics, since their introduction about 50 years ago, has resulted in the evolution and spread of antibiotic resistance with a concomitant increase in the frequency of resistant bacteria (Cohen, 1992, Davies, 1994; Levy, 1992; McCormick, 1998). A consequence of this is that infections previously treatable with antibiotics might require treatment with more expensive or less efficient drugs. Clearly, antibiotic resistance represents a growing threat to public health and is a cause of major medical and economic concern. Whether this unwanted trend can be slowed down or reversed is unclear. That depends on some factors which we can in principle control, such as the volume of antibiotic use, but also on factors outside our control, such as the fitness costs resistance places on bacteria and the rate and extent to which natural selection reduces or eliminates these costs.
