New antibiotics for infections caused by resistant organisms.

A continued increase in the expression of resistance among bacterial pathogens has prompted the development of a variety of new compounds directed against resistant strains of bacteria. Recently, the most dramatic increase in resistance has been among gram-positive organisms, and the predominant areas of development have been within a few classes of agents. Expanded spectrum fluoroquinolones offer advantages against many resistant gram-positive organisms, including S. pneumoniae and S. aureus. Newly developed classes of antimicrobials offer some unique activity against resistant staphylococci and enterococci. The first classes approved for use in the US are the streptogramins, specifically quinupristin/dalfopristin (Synercid), and the oxazolidinone linezolid (Zyvox). Other new classes of agents, including the ketolides, everninomycins, and newer glycopeptides, such as LY-333328, are in the early stages of development.