Antimicrobial resistance among clinical isolates of Streptococcus pneumoniae in North America

From a historical perspective, the development of antibiotic resistance among Streptococcus pneumoniae isolates can be traced over the past 3 decades. In North America, penicillin-resistant pneumococci are now found in nearly all medical centers, but the prevalence of such strains varies by region and time period. In the United States, only approximately 75% of all pneumococci are fully susceptible to penicillin, 15% are intermediately susceptible, and approximately 10% are highly resistant. The latter are often multiply resistant to other unrelated drugs, which leaves few effective chemotherapeutic agents with which to treat serious infections caused by such strains. New approaches to therapy are needed to avoid further selection of antibiotic-resistant mutants; these include discontinuing inappropriate or unnecessary use of antibiotics.