- Objective. To determine the bacteriologic efficacy of ceftriaxone in nonresponsive acute otitis media in children. Methods. In a prospective study 92 patients ages 3 to 36 months (median, 11 months) with culture-proved nonresponsive acute otitis media were studied from January, 1995, through August, 1997. The patients were treated with intramuscular ceftriaxone (50 mg/kg/l/day) for 3 days. Middle ear fluid was aspirated for culture by tympanocentesis on day of enrollment (Day 1); a second tap was performed on Days 4 to 10. Additional middle ear fluid cultures were obtained if clinical relapse occurred. Bacteriologic failure was defined by positive culture on Days 4 to 10. Patients were followed until Day 17 ± 2. Susceptibility was measured by E test. Results. The main drugs administered before enrollment were amoxicillin (38%), amoxicillinclavulanate (25%) and cefaclor (20%). Organisms recovered (n = 105) were: Haemophilus influenzae, 54; Streptococcus pneumoniae, 47; Moraxella catarrhalis, 2; and Streptococcus pyogenes, 2. Thirty-four (72%) of the 47 S. pneumoniae isolates were intermediately resistant to penicillin (MIC 0.1 to 1.0 μg/ml), but all were susceptible to ceftriaxone (MIC < 0.5 μg/ml). Bacteriologic eradication was achieved in 100 of 105 (95%) cases: 54 of 54 (100%) H. influenzae, 43 of 47 (92%) S. pneumoniae, 1 of 2 (50%) M. catarrhalis and 2 of 2 (100%) S. pyogenes. Bacteriologic success (with no relapse) occurred in 13 of 13 (100%) penicillin-susceptible S. pneumoniae vs. 28 of 34 (82%) S. pneumoniae intermediately resistant to penicillin (4 cases of bacteriologic failure and 2 cases of relapse). Conclusion. A 3-day intramuscular ceftriaxone regimen is efficacious for the treatment of non-responsive acute otitis media. The optimal duration of treatment in cases of nonresponsive acute otitis media and whether ceftriaxone is efficacious for the treatment of nonresponsive otitis media caused by S. pneumoniae highly resistant to penicillin is yet to be determined.