title: Pharyngeal colonization prevalence rates for Streptococcus pyogenes and Streptococcus pneumoniae in a respiratory chemoprophylaxis intervention study using azithromycin.
abstract: OBJECTIVE
  A prospective assessment of the pharyngeal colonization prevalence rates for Streptococcus pyogenes and Streptococcus pneumoniae before and after an azithromycin chemoprophylaxis intervention clinical trial in a cohort of US Marine Corps trainees. In addition, the minimum inhibitory concentrations (MICs) for all streptococcal isolates, for azithromycin, penicillin, erythromycin and cefotaxime are reported.
  
  
  METHODS
  Between November 1994 and March 1995, 1108 asymptomatic male US Marine Corps trainees, located in Southern California, were randomly assigned to one of three intervention groups: (1) weekly oral azithromycin, 500 mg (n = 362); (2) 1.2 MU benzathine penicillin G, intramuscularly once (n = 374); or (3) no chemoprophylaxis (n = 372). Subjects provided both a pre- and post-training pharyngeal culture and microbial analysis was conducted to determine the colonization status of each study subject.
  
  
  RESULTS
  The pretraining colonization prevalence was 1.2% for S. pneumoniae and 2.4% for S. pyogenes. There was no statistical difference in pretraining prevalence between the three treatment groups for either organism. Post-training pharyngeal cultures revealed an overall prevalence of 1.1% with no difference between treatment arms. However, the overall post-training prevalence of S. pyogenes colonization increased to 4.8%, with the azithromycin group having significant evidence of protection (0.7%) in comparison with the no-treatment group (8.2%). The Etest method demonstrated no significant difference in the MIC50, MIC90, and MIC ranges between pre- and post-training isolates for any of the tested drugs.
  
  
  CONCLUSIONS
  The use of azithromycin as a chemoprophylactic agent to reduce the colonization and subsequent infection of streptococcal respiratory disease among healthy adult male military recruits may be beneficial.
authors.affiliation: Department of Preventive Medicine and Environmental Health, University of Iowa, Iowa City, Iowa 52241-1008, USA. sputnam@blue.weeg.uiowa.edu
authors.forename: S D
authors.initials: SD
authors.lastname: Putnam
authors.forename: G C
authors.initials: GC
authors.lastname: Gray
authors.forename: D J
authors.initials: DJ
authors.lastname: Biedenbach
authors.forename: R N
authors.initials: RN
authors.lastname: Jones
mesh_terms: D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D017963:Azithromycin / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use*; D015331:Cohort Studies; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000009:adverse effects / Q000494:pharmacology / Q000627:therapeutic use; D010614:Pharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000517:prevention & control; D015995:Prevalence; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000517:prevention & control*; D013290:Streptococcal Infections / Q000453:epidemiology / Q000517:prevention & control*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D013297:Streptococcus pyogenes / Q000187:drug effects* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D010406:Penicillins; D017963:Azithromycin