Over the past 70 years, antibiotic therapy has been successfully used to combat infectious diseases. Nevertheless, the emergence of antibiotic-resistant bacteria is a phenomenon that can plague the effectiveness of the antibiotics employed, which represents a major concern for human and animal health with important socio-economic consequences. Traditionally, most investigations on antibiotic resistance were conducted almost exclusively in the clinical setting. However, now it is well accepted that the current antibiotic resistance found in human pathogens originated from environmental microbes by means of a horizontal transfer of antibiotic resistance genes. The present book aims to focus on the importance of natural environments as diverse as rivers, soils and glaciers for the evolution, maintenance and dissemination of resistance genes. Therefore, the chapters included in this volume will be of interest to those scientists, technologists and graduate students involved in the study of antibiotic resistance from an environmental point of view. Also, it is hoped that the issues addressed in this book will serve to better evaluate the implications of these genes in the formulation of public health policies and strategies. These policies and strategies will then be used to reduce the risks of antibiotic resistance in clinical and nonclinical settings.