title: Impact of azithromycin on oropharyngeal carriage of group A Streptococcus and nasopharyngeal carriage of macrolide-resistant Streptococcus pneumoniae.
abstract: BACKGROUND
  Invasive group A streptococcal (GAS) infections are a cause of serious morbidity and high mortality. There is a need for a simple, effective antimicrobial regimen that could be used to prevent invasive GAS disease in high risk situations. To assess azithromycin as a chemoprophylactic agent, we evaluated its efficacy for eradication of oropharyngeal (OP) GAS and its impact on the nasopharyngeal (NP) colonization rate of macrolide-resistant Streptococcus pneumoniae.
  
  
  METHODS
  We obtained OP and NP swabs for GAS and pneumococcus culture, respectively, from 300 schoolmates of a child with an invasive GAS infection. GAS culture-positive students were treated with daily azithromycin (12 mg/kg/day) for 5 days. We obtained follow-up OP and NP swabs at 9 (Day 17) and 24 (Day 32) days post-treatment from those students identified as GAS carriers on Day 0 and determined macrolide susceptibility of GAS and pneumococcal isolates.
  
  
  RESULTS
  Of the 300 students swabbed 152 (50%) carried GAS in their oropharynx. On Day 17, efficacy of azithromycin for GAS eradication was 95% (140 of 147) for all students. NP colonization rates for pneumococci decreased from 46% (67 of 146) to 12% (17 of 144; P < 0.001) by Day 17 and to 20% (27 of 137; P < 0.001) by Day 32. The prevalence of erythromycin-resistant pneumococcal isolates increased from 2% (3 of 146) to 4% (6 of 144) by Day 17 and to 8% (11 of 137; P = 0.04) by Day 32.
  
  
  CONCLUSIONS
  Azithromycin is an effective short course regimen for eradication of oropharyngeal GAS. However, azithromycin selected for macrolide-resistant strains of pneumococci. These findings highlight the importance of determining the appropriate circumstances for antimicrobial prophylaxis to prevent invasive GAS infections.
authors.affiliation: National Center for Infectious Diseases, Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Morita
authors.forename: E
authors.initials: E
authors.lastname: Kahn
authors.forename: T
authors.initials: T
authors.lastname: Thompson
authors.forename: L
authors.initials: L
authors.lastname: Laclaire
authors.forename: B
authors.initials: B
authors.lastname: Beall
authors.forename: G
authors.initials: G
authors.lastname: Gherardi
authors.forename: K L
authors.initials: KL
authors.lastname: O'Brien
authors.forename: B
authors.initials: B
authors.lastname: Schwartz
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D017963:Azithromycin / Q000008:administration & dosage*; D002353:Carrier State / Q000382:microbiology; D016009:Chi-Square Distribution; D002648:Child; D015169:Colony Count, Microbial; D016001:Confidence Intervals; D004334:Drug Administration Schedule; D004352:Drug Resistance, Microbial; D005260:Female; D006801:Humans; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D009960:Oropharynx / Q000382:microbiology; D011008:Pneumococcal Infections / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology; D013290:Streptococcal Infections / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000302:isolation & purification; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin