Telithromycin and quinupristin-dalfopristin resistance in clinical isolates of Streptococcus pyogenes:: SMART program 2001 data

This study evaluated the current status of antimicrobial resistance in clinical isolates of Streptococcus pyogenes in Taiwan as part of the SMART (Surveillance from Multicenter Antimicrobial Resistance in Taiwan) program. In 2001, 419 different isolates of S. pyogenes, including 275 from respiratory secretions, 87 from wound pus, and 31 from blood, were collected from nine hospitals in different parts of Taiwan. MICs of 23 antimicrobial agents were determined at a central location by the agar dilution method. All of the isolates were susceptible to penicillin (MIC at which 90% of the isolates were inhibited [MIC90], less than or equal to0.03 mug/ml), cefotaxime (MIC90, less than or equal to0.03 mug/ml), cefepime (MIC90, 0.06 mug/ml), meropenem (MIC90, less than or equal to0.03 mug/ml), moxifloxacin (MIC90, 0.25 mug/ml), vancomycin (MIC90, 0.5 mug/ml), and linezolid (MIC90, 1 mug/ml). Overall, 78% of isolates were not susceptible to erythromycin (54% were intermediate, and 24% were resistant), and 5% were not susceptible to clindamycin. Of the 101 erythromycin-resistant isolates, 80.2% exhibited the M phenotype (mefA gene positive), 18.9% exhibited the cMLS (constitutive resistance to macrolides-lincosamides-streptogramin B [MLS]) phenotype (ermB gene positive), and 1% exhibited the iMLS (inducible resistance to MLS) phenotype (ermB gene positive). Fluoroquinolones (sitafloxacin > moxifloxacin > ciprofloxacin = levofloxacin = gatifloxacin > gemifloxacin) demonstrated potent activity against nearly all of the isolates of S. pyogenes tested. Thirty-two isolates (8%) were not susceptible to quinupristin-dalfopristin. Seventeen percent of isolates had telithromycin MICs of greater than or equal to1 mug/ml, and all of these isolates exhibited erythroinycin MICs of greater than or equal to32 mug/ml. The high prevalence of resistance to telithromycin (which is not available in Taiwan) limits its potential use in the treatment of S. pyogenes infections, particularly in areas with high rates of macrolide resistance.