INTRODUCTION TO ANTIMICROBIAL AGENTS
Antimicrobial agents are among the most dramatic examples of the advances of modern medicine. Many infectious diseases once considered incurable and lethal are now amenable to treatment with a few pills. The remarkably powerful and specific activity of antimicrobial drugs is due to their selectivity for targets that are either unique to microorganisms or much more important in them than in humans. Among these targets are bacterial and fungal cell wall-synthesizing enzymes (see Chapters 43 and 48), the bacterial ribosome (see Chapters 44and 45), the enzymes required for nucleotide synthesis and DNA replication (see Chapter 46), and the machinery of viral replication (see Chapter 49). The special group of drugs used in mycobacterial infections is discussed in Chapter 47. The much older and less selective cytotoxic antiseptics and disinfectants are discussed in Chapter 50. The clinical uses of all these agents are presented in Chapter 51.
Microorganisms can adapt to environmental pressures in a variety of effective ways, and their response to antibiotic pressure is no exception. An inevitable consequence of antimicrobial usage is the selection of resistant microorganisms, perhaps the most obvious example of evolution in action. Overuse and inappropriate use of antibiotics has fueled a major increase in prevalence of multidrug-resistant pathogens, leading some to speculate that we are nearing the end of the antibiotic era. Unfortunately, as the need has grown in recent years, development of novel drugs has slowed. The most vulnerable molecular targets of antimicrobial drugs have been identified, and in many cases crystallized and characterized. Pending the identification of new targets and compounds, it seems likely that over the next decade we will have to rely on currently available families of drugs. In the face of continuing development of resistance, considerable effort will be required to maintain the effectiveness of these drug groups.