Antimicrobial resistance with Streptococcus pneumoniae: much ado about nothing?

During the past decade in the United States, Streptococcus pneumoniae has changed dramatically in the context of antimicrobial resistance. Resistance to multiple different antibiotic classes including beta-lactams (penicillins, cephalosporins, and beta-lactamase inhibitor combinations), macrolides, clindamycin, the tetracyclines, chloramphenicol, and trimethoprim-sulfamethoxazole (TMP/SMX) has emerged at high rates with this important respiratory tract pathogen. There is no question that the in vitro activity of these antimicrobial agents is substantially lower for many strains of S. pneumoniae than it was even a few years ago. The larger question is, however, what does this decrease in activity mean from a clinical perspective? Stated another way, does resistance defined according to current standards in the laboratory, translate into diminished effectiveness when these agents are used to treat patients with pneumococcal infections? It is this question that serves as the principal basis for this review.