Susceptibility of group A beta-hemolytic streptococci to thirteen antibiotics: examination of 301 strains isolated in the United States between 1994 and 1997.

ABSTRACT

BACKGROUND: Because of continuing reports from many countries of increasing resistance of group A streptococci to macrolide antibiotics, we determined the antibiotic susceptibility of recent group A streptococcal isolates from the United States. METHODS: We evaluated 301 Streptococcus pyogenes isolates (245 from patients with uncomplicated pharyngitis and 56 isolates from patients with invasive systemic infections) for susceptibility using the Etest technique. The isolates came from 24 states and the District of Columbia during the years 1994 through 1997. Thirteen antibiotics (azithromycin, ceftriaxone, cephalothin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, imipenem, levofloxacin, oxacillin, penicillin G, tetracycline and trimethoprim-sulfamethoxazole) were studied. RESULTS: The MIC90 for penicillin was 0.016 microg/ml, which is not significantly different from previous reports. Of the 301 isolates only 2.6% were resistant to a macrolide antibiotic and only 4% were resistant to tetracycline. CONCLUSIONS: These data indicate that antibiotic resistance among recent isolates of group A streptococci (including those from patients with severe infections) currently is not a clinically significant problem in the United States.