• Use of antimicrobials and carriage of penicillin-resistant pneumococci in children : repeated cross-sectional studies covering 10 years [PhD Thesis]

      Vilhjálmur Ari Arason (Háskólaútgáfan, 2006-10-01)
      Objectives: The overall aim of this thesis was to analyse the use of antimicrobials in pre-school children in Iceland and the connection between such use and the carriage of penicillin-nonsusceptible pneumococci(PNSP). Study populations and methods: Prescription data and medical histories from 2,612 children, aged 1 to 6 years, living in different geographically welldefined study areas in Iceland, and nasopharyngeal specimens from 2,486 children were analysed in three crosssectional studies covering 10 years (Phase I 1993, II 1998, and III 2003). Participation varied from 75% to 88%. Annual analysis of oral antimicrobial sales/prescriptions for whole communities (hospital use excluded) were based on 22,132 prescriptions in 1993, and 15,153 in 1998. Main outcome measures: The prevalence and risk factors for nasopharyngeal carriage of PNSP, total antimicrobial use, antimicrobial use for acute otitis media (AOM), parental expectations and tympanostomy tube placements. Results: • Antimicrobial prescription rates among GPs diminished by about 1/3 over the study period. Prescription habits varied greatly between communites especially because of AOM. • Parents’ expectations of antimicrobial prescriptions were associated with the antimicrobial prescription rate in each area. • The cumulative prevalence of tympanostomy tube placement among pre-school children is high in Iceland (over 30%). In vi areas where the prescription rate was high, broad-spectrum antimicrobials were prescribed relatively more often than in other areas, and the tympanostomy tube placement rate was increasing (up to 44% of all children). In other areas, tympanostomy tube rate among children deceased (down to 17%) at the same time as antimicrobial use for AOM diminished. • There was a strong association between antimicrobial use on the individual level and the nasopharyngeal carriage of PNSP. • PNSP, multiresistant, serotype 6B (phenotypically identical to the Spain6B-2 clone) appeared and disappeared over a 10-year period, in communities with both high and low antimicrobial use. Conclusions: There is a strong association between antimicrobial use for individual children and the nasopharyngeal carriage of PNSP. Pneumococcus is acquired from other children, usually in day-care settings and PNSP selectively colonised when receiving antimicrobials. Spread of novel resistant clones appears to be the main reason for marked changes in pneumococcal resistance rates in individual communities over time. Antimicrobial drug (over)use for AOM my be associated with future episodes of AOM and tympanostomy tube placements.