Background. Acute otitis media is the leading reason for antibiotic prescriptions in childhood. The increase in antibiotic resistance of Streptococcus 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 nasopharyngeal carriage of S. pneumoniae during antibiotic therapy prescribed for acute otitis media.
Methods. Between October, 1993, and March, 1994, we conducted a clinical trial comparing cefpodoxime-proxetil and amoxicillin-clavulanate in acute otitis media. From 364 children, 4 months to 4.5 years old, a nasopharyngeal sample was obtained before and after treatment. Antibiotic susceptibility was established by determining minimal inhibitory concentrations by the agar dilution method. Serotype and randomly amplified polymorphic DNA analysis were used to compare pre- and posttreatment S. pneumoniae strains.
Results. The risk for a child to carry penicillin-resistant S. pneumoniae (MIC ≥ 0.125 mg/l) did not increase after antibiotic treatment: 84 of 364 (23.1%) before, 70 of 364 (19.2%) after. There was a significant decrease of penicillin-susceptible S. pneumoniae carriage, 117 of 364 (32.1%) before treatment compared with 24 of 364 (6.6%) (P = 0.0001) after treatment. However, among the children carrying S. pneumoniae at the end of the treatment there was an increase in the percentage of 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 pneumococcus before, 16 carried another genotypically different serotype and 56 harbored the same serotype. Among these 56 children 2 patients harbored strains that had increased MICs for the tested beta-lactam antibiotics. The randomly amplified polymorphic DNA analysis showed that in one case, the strains were genetically different.
Conclusions. These data illustrate that antibiotic therapy did not increase the rate at which children carried penicillin-resistant S. pneumoniae, but there was an increase in the rate of resistance among the children carrying pneumococci at the end of the treatment, mainly as a result of reduction of susceptible strains.
From the Microbiology Laboratory, CHI, Créteil (RC, PG); Microbiology Laboratory, Robert Debré Hospital, Paris (EB,NB); Microbiology Laboratory, Hotel Dieu Hospital, Paris (EV); Association Clinique et Thérapeutique Infantile du Val de Marne (FLR, CL, MB); and Association Française de Pédiatrie Ambulatoire, Lyon (JL), France.
Accepted for publication Feb. 12, 1997.
Presented in part at the 35th Interscience Conference on Antimicrobial Agents and Chemotherapy, September 188 to 20, 1995, San Francisco (Abstract C7).
Address for reprints: Robert Cohen, M.D.. CHI Créteil, Service de Microbiologie, 40 avenue de Verdun, 94000 Créteil, France. Fax (33) 1 45 17 53 49; E-mail firstname.lastname@example.org.