Increased carriage of resistant non-pneumococcal alpha-hemolytic streptococci after antibiotic therapy

J Pediatr. 1999 Nov;135(5):618-23. doi: 10.1016/s0022-3476(99)70061-2.


Objective: We compared colonization and resistance rates of non-pneumococcal alpha-hemolytic streptococci (AHS) and Streptococcus pneumoniae in children receiving antibiotic therapy for acute otitis media.

Study design: Between December 1997 and September 1998, children 6 months to 6 years of age, diagnosed with acute otitis media were randomly assigned to receive amoxicillin/clavulanate (Augmentin) 45 mg/kg/d in 2 divided doses for 10 days or azithromycin (Zithromax), 10 mg/kg, once on the first day, followed by 5 mg/kg daily for 4 days. Nasopharyngeal swabs for culture were obtained before and at 2 weeks and 2 months after the start of therapy. Streptococci were identified by species, and antibiotic susceptibility was determined by the epsilometric test.

Results: One hundred six children completed the 2-week follow-up and 2-month follow-up, respectively. The nasopharyngeal carriage rate of non-pneumococcal AHS increased from 14% before treatment to 32% at the 2-week follow-up (P =.02) and was similar in both treatment groups. In contrast, the carriage of S pneumoniae decreased from 51% before therapy to 27% at the 2-week follow-up (P =.002). The carriage of penicillin-resistant AHS strains (minimum inhibitory concentration > 1 microg/mL) increased from 9% before treatment to 26% at 2 weeks and 36% at 2 months.

Conclusions: Amoxicillin/clavulanate and azithromycin therapy resulted in increased isolation of nasopharyngeal non-pneumococcal AHS, many of which were multidrug-resistant, in contrast to a decrease in pneumococcal carriage. This suggests that the competitive balance between these 2 groups of organisms was disturbed as a result of differential antibiotic susceptibility. The importance of drug-resistant AHS as a reservoir for resistance genes for S pneumoniae warrants further investigation.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amoxicillin-Potassium Clavulanate Combination / therapeutic use
  • Anti-Bacterial Agents / therapeutic use*
  • Azithromycin / therapeutic use
  • Child, Preschool
  • Drug Resistance, Multiple
  • Drug Therapy, Combination / therapeutic use
  • Female
  • Humans
  • Infant
  • Male
  • Nasopharynx / microbiology
  • Otitis Media / drug therapy
  • Streptococcus / drug effects*
  • Streptococcus / isolation & purification
  • Streptococcus pneumoniae / drug effects
  • Streptococcus pneumoniae / isolation & purification
  • beta-Lactam Resistance


  • Anti-Bacterial Agents
  • Amoxicillin-Potassium Clavulanate Combination
  • Azithromycin