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766 OTITIS MEDIA (OM) WITHIN 30 DAYS OF DIAGNOSIS: RECURRENCE OR REINFECTION?

We performed a prospective study of clinical recurrences (CR) of OM within the first 30 days after diagnosis. The purpose was to identify risk factors for CR and to determine if the CR was a bacteriologic recurrence (same pathogen as the acute episode) or a reinfection (different bacterial species or different strain of the same species). Patients were treated initially with Augmentin, Cefaclor or Trimethoprim-sulfamethoxazole. Tympanocentesis was performed at diagnosis, after 3-5 days of therapy and at the time of CR. Streptococcus pneumonias were classified by capsular serotypes; Haemophilus influenzae strains by biotypes and outer membrane protein electrophoresis patterns.Results: 36/105 patients (34%) developed CR. 29 underwent repeat tympanocentesis. 21/25 patients (84%) had reinfection; 4/25 (16%) were infected with the same pathogen. No pathogen could be identified initially or at CR in 4. Age, sex, race or presence of MEE at the end of therapy did not identify those with CR. Children with CR were more likely to have 3 episodes of OM in the last 6 months (40% vs. 12%, p = .003).Conclusions: 1) History of recurrent OM is a risk factor for clinical recurrences. 2) Clinical recurrences within 30 days of diagnosis are usually reinfections. Pediatricians should not assume that clinical recurrences after therapy are failures of initial antibiotic therapy.