Objectives. The PROTEKT US surveillance program (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin in the United States) commenced in 2000 to document the emergence and spread of antimicrobial resistance among respiratory tract pathogens in the United States.

Methods. During 2000–2001, 206 centers from 154 cities/metropolitan areas collected 16,727 clinical isolates (Streptococcus pneumoniae, n=10103, Streptococcus pyogenes, n=3918, Haemophilus influenzae, n=2706).

Results. Among S. pneumoniae isolates, 38.9% showed decreased susceptibility to penicillin (12.5% intermediate, 26.4% resistant) with marked geographical variability. The erythromycin resistance rate was 31.0% and highly correlated with penicillin resistance. The rate of fluoroquinolone resistance was 0.8%. Telithromycin was nearly uniformly active against S. pneumoniae (MIC₉₀ 0.5 mg/l). All isolates of S. pyogenes were penicillin-susceptible, 5.5% were resistant to erythromycin. Telithromycin minimum inhibitory concentrations (MICs) were lower than clindamycin and macrolide MICs against S. pyogenes (MIC₉₀ 0.03 mg/l versus 0.25 mg/l and 0.12 mg/l, respectively). 28.3% of H. influenzae isolates produced β-lactamase. Telithromycin activity versus H. influenzae was not affected by β-lactamase production.

Conclusions. The PROTEKT US study confirms the widespread prevalence of antimicrobial resistance among common bacterial respiratory pathogens in the US, and re-affirms the importance of continued surveillance to guide optimum empiric therapy for patients with Community-acquired respiratory tract infections (CARTIs). The new ketolide, telithromycin, maintained potent activity against study isolates in vitro and offers promise for the effective treatment of CARTIs.