title: Individual-level effects of antibiotics on colonizing otitis pathogens in the nasopharynx.
abstract: BACKGROUND
  Although there is evidence of an association between antibiotic consumption and resistant bacteria on a population level, the relationship on an individual level has been less well studied, particularly in terms of nasopharyngeal colonization. We have therefore analysed this association, using data from a closely followed cohort of children taking part in a vaccination trial.
  
  
  METHODS
  109 children with early onset of acute otitis media (AOM) were randomised to heptavalent pneumococcal conjugate vaccine (PCV7) or no vaccination. They were followed for three years with scheduled appointments as well as sick visits. Nasopharyngeal cultures were obtained at all visits. Antibiotic treatments were recorded, as were risk factors for AOM, including siblings, short breast-feeding and parental smoking. Data were entered into a Cox regression model, and the findings of Streptococcus pneumoniae and Haemophilus influenzae with reduced susceptibility to the penicillin group were related to the number of previous courses of antibiotics.
  
  
  RESULTS
  There was evidence of an association between the amount of previously consumed betalactams and colonization with beta-lactamasenegative ampicillin-resistant (BLNAR) H. influenzae (RR 1.21; 95% CI 1.03-1.43; p = 0.03), and also with the most commonly prescribed drug; amoxicillin (RR 1.39; 95% CI 1.09-1.76; p = 0.01). There was no evidence for an association between antibiotic consumption and betalactamase producing H. influenzae or S. pneumoniae with reduced susceptibility to penicillin. Furthermore, there was no evidence of an association between resistant bacteria and AOM risk factors or PCV7.
  
  
  CONCLUSIONS
  In this subgroup of children, most of whom were given several courses of antibiotics in early childhood, there was evidence of an association between betalactam/amoxicillin consumption and nasopharyngeal colonization with BLNAR strains, bacteria that have increased in prevalence during the last 10-15 years, and that are notoriously difficult to treat with oral antibiotics.
authors: Dpt of Otorhinolaryngology, Head and Neck Surgery, Lund University Hospital, Sweden. Electronic address: marie.gisselsson-solen@med.lu.se.
authors: Marie
authors: M
authors: Gisselsson-Solen
authors: Dpt of Otorhinolaryngology, Head and Neck Surgery, Lund University Hospital, Sweden.
authors: Ann
authors: A
authors: Hermansson
authors: Dept. of Medical Sciences, Section of Clinical Bacteriology, Uppsala University, Sweden.
authors: Åsa
authors: Å
authors: Melhus
mesh_terms: D000658:Amoxicillin / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002675:Child, Preschool; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D005500:Follow-Up Studies; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000627:therapeutic use*; D006801:Humans; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology*; D010033:Otitis Media / Q000188:drug therapy* / Q000382:microbiology; D065093:beta-Lactamase Inhibitors / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D065093:beta-Lactamase Inhibitors; D000658:Amoxicillin
keywords: Acute otitis media; Antibiotic resistance; BLNAR; Haemophilus influenzae; Nasopharyngeal colonization; Streptococcus pneumoniae