Since the mid-1990s, there has been the recognition of a very disturbing trend of antibiotic resistance among a wide variety of pathogens that are causing serious disease in patients residing in the community, in long-term care facilities, and in hospitals. A partial list consists of the following bacteria: Streptococcus pneumoniae, resistant to penicillin, first- and second-generation cephalosporins, macrolides azilides, tetracyclines, trimethoprim–sulfamethoxazole (TMP- SFX), and fluoroquinolones; Staphylococcus aureus, resistant to oxacillin, cephalosporins, clindamycin, fluoroquinolones, and, very rarely, vancomycin; ampicillin and vancomycinresistant Enterococcus spp.; extended-spectrum β-lactamase–producing Escherichia coli and Klebsiella pneumoniae resistant to broad-spectrum cephalosporins; Salmonella spp., resistant to ampicillin, chloramphenicol, TMP–SFX, fluoroquinolones, and third-generation cephalosporins; Campylobacter spp., resistant to fluoroquinolones; Helicobacter pylori, resistant to clarithromycin; Vibrio cholerae, resistant to ciprofloxacin; aminoglycoside and fluoroquinolone-resistant Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Acinetobacter spp.; clindamycinresistant Bacteroides fragilis; and Mycobacterium tuberculosis organisms resistant to all available drugs.

The pharmaceutical companies have responded to this grave concern and have developed several new agents (quinupristin–dalfopristin, linezolid, daptomycin, and dalbavancin) that inhibit the growth of gram-positive bacteria, and a new compound, tigecycline, that possesses inhibitory activity for a wide range of gram-positive, gram-negative, and anaerobic bacteria. Although some data are available, it is premature to precisely establish the indications for these new antibiotics, their potential to cause toxicities and drug–drug interactions, and to identify the preferred agent for a specific infection.