Resistance among Streptococcus pneumoniae: patterns, mechanisms, interpreting the breakpoints.

Streptococcus pneumoniae is a frequent cause of respiratory tract infections. In the United States and worldwide, antimicrobial resistance of S pneumoniae has complicated the management of infections caused by this organism. In the United States, antimicrobial resistance with S pneumoniae has evolved almost entirely during the 1990s. Resistance currently exists at high rates with beta-lactams, macrolides, tetracyclines, chloramphenicol, and trimethoprim/sulfamethoxazole. Multiresistant strains--strains that are resistant to penicillin plus at least 2 other antimicrobial classes--are also increasing in prevalence. Fluoro-quinolone resistance remains at low levels in the United States. Control of the problem of antimicrobial resistance will require more judicious and appropriate use of antimicrobials, the development of new agents with novel targets of action, and strategies for preventing disease from occurring in the first place. In addition, the pursuit of an understanding of resistance mechanisms and pharmacodynamics as they relate to clinical outcome must be an ongoing effort, and that knowledge must be applied to the development of more effective approaches for the treatment of infections caused by S pneumoniae.