CHANGE IN NASOPHARYNGEAL CARRIAGE OF STREPTOCOCCUS-PNEUMONIAE RESULTING FROM ANTIBIOTIC-THERAPY FOR ACUTE OTITIS-MEDIA IN CHILDREN

Background, Acute otitis media is the leading reason for antibiotic pr escriptions in childhood, The increase in antibiotic resistance of Str eptococcus pneumoniae is generally attributed to the extensive use of antibiotics and the selective pressure on the bacterial strains of the nasopharyngeal flora, Objective, To evaluate the change in nasopharyn geal carriage of S. pneumoniae during antibiotic therapy prescribed fo r acute otitis media, Methods, Between October, 1993, and March, 1994, we conducted a clinical trial comparing cefpodoxime-proxetil and amox icillin-clavulanate in acute otitis media, From 364 children, 4 months to 4.5 years old, a nasopharyngeal sample was obtained before and aft er treatment. Antibiotic susceptibility was established by determining minimal inhibitory concentrations by the agar dilution method, Seroty pe and randomly amplified polymorphic DNA analysis were used to compar e pre- and posttreatment S. pneumoniae strains, Results, The risk for a child to carry penicillin-resistant S. pneumoniae (MIC greater than or equal to 0.125 mg/I) did not increase after antibiotic treatment: 8 4 of 364 (23.1%) before, 70 of 364 (19.2%) after, There was a signific ant decrease of penicillin-susceptible S. pneumoniae carriage, 117 of 364 (32.1%) before treatment compared with 24 of 364 (6.6%) (P = 0.000 1) after treatment, However, among the children carrying S. pneumoniae at the end of the treatment there was an increase in the percentage o f penicillin-resistant pneumococci: 84 of 201 (41.8%) before treatment and 70 of 94 (74.5%) after treatment, Among the 94 children carrying S. pneumoniae at the end of the treatment, 22 did not harbor pneumococ cus before, 16 carried another genotypically different serotype and 58 harbored the same serotype, Among these 56 children 2 patients harbor ed strains that had increased MICs for the tested beta-lactam antibiot ics, The randomly amplified polymorphic DNA analysis showed that in on e case, the strains were genetically different, Conclusions, These dat a illustrate that antibiotic therapy did not increase the rate at whic h children carried penicillin-resistant S. pneumoniae, but there was a n increase in the rate of resistance among the children carrying pneum ococci at the end of the treatment, mainly as a result of reduction of susceptible strains.