Resistance among Streptococcus pneumoniae: Patterns, mechanisms, interpreting the breakpoints

Streptococcus pneumoniae is a frequent cause of respiratory tract infection s. In the United States and worldwide, antimicrobial resistance of S pneumo niae has complicated the management of infections caused by this organism. In the United States, antimicrobial resistance with S pneumoniae has evolve d almost entirely during the 1990s. Resistance currently exists at high rat es with beta -lactams, macrolides, tetracyclines, chloramphenicol, and trim ethoprim/sulfamethoxazole. Multiresistant strains -strains that are resista nt to penicillin plus at least 2 other antimicrobial classes-are also incre asing in prevalence. Fluoro-quinolone resistance remains at low levels in t he United States. Control of the problem of antimicrobial resistance will r equire more judicious and appropriate use of antimicrobials, the developmen t of mew 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 a pplied to the development of more effective approaches for the treatment of infections caused by S pneumoniae.