Over the last 50 years, the rapid increase in the use of antibiotics, not only in people, but also in animal husbandry and agriculture, has delivered a selection unprecedented in the history of evolution. Consequently, society is facing one of its gravest public health problems-the emergence of infectious bacteria with resistance to many, and in some cases all, available antibiotics. This book brings together a multidisciplinary group of experts to discuss this problem. It begins by examining the origins of resistance and goes on to look at how the use of antibiotics in human medicine and farming/agriculture has selected for resistant bacteria. Separate chapters describe the evolution of resistance determinants and how these are spread both within and between bacterial species. Finally, the book contains discussions on strategies for countering the threat of antibiotic resistance. A major re-thinking of our approach to the treatment of infectious diseases is proposed-that antibiotic resistance should be seen as a problem created by the disruption of normal microbial ecology. To restore efficacy to earlier antibiotics, and to maintain the success of new antibiotics that are introduced, we need to use these drugs in a way that ensures an ecological balance that favours the predominance of susceptible bacteria.