Microbiological and Pharmacodynamic Considerations in the Treatment of Infection Due to Antimicrobial-Resistant Streptococcus pneumoniae

The incidence of antimicrobial-resistant strains of Streptococcus pneumoniae has increased alarmingly in recent years. The problem is exacerbated by the global spread of resistant organisms. Currently, the incidence of penicillin-resistant pneumococci isolated from clinical specimens in the United States is>35%. For empirical oral treatment of community-acquired respiratory infections, 3 choices are available: b-lactam agents, macrolides, and ¯uoroquin-olones. In considering the therapeutic ef®cacy of these agents, it is essential to also take pharmacokinetic and pharmacodynamic (PK/PD) factors into account. Many drugs are ef-fective against penicillin-susceptible strains. However, the higher the minimum inhibitory con-centration of penicillin, the more likely that cross-resistance to b-lactam agents and macrolides will occur. Currently, the incidence of ¯uoroquinolone-resistant pneumococci is low; it is proposed that adequate dosing based on the PK/PD properties of ¯uoroquinolones may help reduce the emergence of resistant organisms. Prudent use of all antimicrobials is essential to decrease the emergence of strains resistant to these agents. The emergence of penicillin-resistant strains of Streptococcus pneumoniae was ®rst documented in the late 1960s and earl