Impact of Ketolides on Resistance Selection and Ecologic Effects during Treatment for Respiratory Tract Infections

Ketolides are a new class of antibacterials that have been specifically developed for the treatment of community- acquired respiratory tract infections in an era of increasing resistance among major etiologic pathogens. These agents possess several unique structural features, including a 3–keto function and a large aromatic side chain, that confer not only a mode of action that differentiates them from the macrolide class but also a reduced potential to induce—or select for—resistant strains. Studies also suggest that ketolides such as telithromycin have a lower ecologic impact on the body’s microflora than agents such as clarithromycin and amoxicillin–clavulanate, potentially reducing the risk of emergence of resistant strains and the spread of such resistance to pathogenic species. Therefore, available evidence suggests that ketolides may not only provide important new treatment options in an era of increasing resistance but may also contribute to reducing the pressure for development of further resistance. Clearly, further studies are required to confirm this low resistance potential once the ketolide agents become more widely used in routine practice.