Increasing prevalence of antimicrobial resistance among isolates of Streptococcus pneumoniae from the PROTEKT surveillance study, and comparative in vitro activity of the ketolide, telithromycin

Abstract

The prevalence of resistance to a range of antimicrobials was determined for isolates of Streptococcus pneumoniae examined in the PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) surveillance study (1999-2000) using NCCLS testing methods and interpretative criteria. Of 3362 pneumococcal isolates collected from 69 centres in 25 countries, 22.1 % overall were resistant to penicillin G, with the highest rates of resistance found among isolates from Asia (53.4%), France (46.2%) and Spain (42.1%). Erythromycin A resistance occurred in 31.1% of isolates overall with the highest rates found in Asia (79.6%), France (57.6%), Hungary (55.6%) and Italy (42.9%). Marked geographical differences in the prevalence of both penicillin G (the Netherlands 0%; South Korea 71.5%) and erythromycin A (Sweden 4.7%; South Korea 87.6%) resistance were observed. Asia was characterized by the highest prevalence of resistance, overall, with only eight of 19 antimicrobials (co-amoxiclav, linezolid, vancomycin, telcoplanin, quinupristin/dalfopristin, levofloxacin, moxifloxacin and telithromycin) retaining high activity against isolates of S. pneumoniae from this region. Notable rates of resistance to clarithromycin, azithromycin, co-trimoxazole and tetracycline were observed in the majority of countries submitting isolates of S. pneumoniae to the PROTEKT surveillance study. Fluoroquinolone resistance was low (1%), overall, although 14.3% of 70 isolates from Hong Kong were resistant to levofloxacin and moxifloxacin, all but one of these isolates belonging to a single clone of the 23F serotype. Although, at present, apparently limited to pockets of clonal spread, continued vigilance with regard to the evolution of fluoroquinolone resistance is indicated. Telithromycin (MIC90 0.12 mg/L; 99.9% of isolates susceptible) and linezolid (MIC90 2 mg/L; 100% of isolates susceptible) were the two most active oral agents tested, both compounds retaining activity against isolates of fluoroquinolone-resistant S. pneumoniae. The results of the PROTEKT surveillance study 1999-2000 emphasize the widespread evolution of resistance to a variety of antimicrobials amongst isolates of S. pneumoniae and demonstrate the potential of telithromycin as a therapeutic option for the treatment of community-acquired respiratory tract infections caused by this organism.