Drug options for treatment of infections are increasingly limited. The pharmaceutical industry has found it difficult to discover new antimicrobial agents, and only two novel classes of antibiotics, the oxazolidinones and the cyclic lipopeptides, have entered the market since the late 1960s. Few new agents have reached the market in the last decade with potential interest for community-acquired pneumonia (CAP) treatment, including linezolid (the first oxazolidinone in clinical use), new fluoroquinolones, cefditoren, ertapenem, and telithromycin. Agents currently in clinical development include other novel quinolones and ketolides, broad-spectrum cephalosporin derivatives, faropenem, several glycopeptides, and iclaprim. Other molecules are considered to be promising candidates for the future. In addition to the foregoing agents, alternative treatment approaches have also been introduced into clinical practice, which include the administration of the appropriate antimicrobials in a timely manner and the consideration of the pharmacokinetic-pharmacodynamic properties of the agent(s).Antibiotics are an essential part of modern medicine and represent the second most commonly prescribed category of drugs. The downside is that the more an antibiotic is used, the more resistance to it spreads. Eventually, resistance rises to such a level that it reduces the efficacy of the drug in a human population, forcing clinicians to try other antimicrobial agents. In response to bacterial resistance, the pharmaceutical industry has produced a remarkable range of effective new therapies. Yet, if the development of antibiotics is reviewed, it is clear that the current rate of discovery is far lower than in the 1940s through the 1960s, when all the major families of compounds were identified. The last novel class of antibacterials prior to the year 2000-trimethoprim-was described in 1968, and the majority of antimicrobials introduced since then have been derivatives of previously discovered classes of drugs. But, unfortunately, the number of chemical modifications that can be made to an old molecule is limited and, over time, this route will fade away. Molecular biology and genomics have not yet proved fruitful in the discovery of new antimicrobial agents, 1 and some researchers are now focusing on drugs that turn off the production or antagonize the activity of virulence factors, possibly as
