Antimicrobial agents are used to treat infections involving biological agents (pathogens) other than humans and the goal is to rid the host of the pathogen. Because of the involvement of a second living agent in the Host-Pathogen-Antimicrobial agent triangle, drug therapy is affected by the biological characteristics of the pathogen including its tissue specificity and most importantly the changes it undergoes to survive while being exposed to the antimicrobial agent. It has become very clear that the drugs that are used to treat infections allow the pathogens to enhance their capability to become resistant and furthermore transfer this resistance to other pathogens. Only appropriate and judicious use of anti-infectives can prolong their effectiveness.
This chapter will provide an overview of the historical perspective and current antimicrobial agents. This will be followed by a discussion on the recently developed antimicrobial agents, those that are in development, including those with novel mechanisms of action.