Pathogens isolated during treatment failures in otitis.

Objectives: A prospective study in the Paris region to evaluate the clinical and bacteriologic epidemiology of acute otitis media in infants in whom oral antibiotic therapy resulted in clinical failure.

Methods: The study included 186 children with a mean age of 17.5 +/- 13.1 months. Two-thirds of them attended a day-care center and 40.8% had a history of recurrent otitis media. The most frequently prescribed prior antibiotics were amoxicillin-clavulanic acid (43% of cases), an oral third generation cephalosporin (22.6%), erythromycin-sulfisoxazole (11.8%) and a first generation cephalosporin (10.2%). The average duration of antibiotic therapy was 6.9 +/- 2.65 days. Specimens for bacterial cultures included 188 samples of middle ear fluid obtained by tympanocentesis and 37 collected from otorrhea fluid.

Results: One hundred forty-one samples (62.7%) from 126 children yielded 170 bacterial isolates. In 60 children (32.3%) the culture of the ear pus was sterile. Among the 170 bacterial isolates: 67 (39.4%) were Streptococcus pneumoniae (59 patients), of which 77.6% had reduced susceptibility to penicillin (PRSP with penicillin MIC > or = 0.125 mg/l); 61 (35.9%) were Haemophilus influenzae (56 patients) of which 49.2% were beta-lactamase producers; and 8 were Moraxella catarrhalis (8 patients), of which 87.5% were beta-lactamase producers. Thirty-six patients were infected by S. pneumoniae with penicillin MIC > or =1 mg/l. In our study attending day-care center (P = 0.04), temperature >38 degrees C with signs of otalgia (P = 0.02), age <2 years (P = 0.048) and prior antibiotic treatment with erythromycin-sulfisoxazole (P = 0.006) were independently predictive risk factors for patients infected with penicillin-resistant S. pneumoniae. Pneumococcal serogroups 23, 14 and 19 were predominant (25.4, 25.4 and 23.8%, respectively). Penicillin resistance was mainly associated with serogroups 23 and 14.

Conclusions: Penicillin-resistant S. pneumoniae isolates are frequently responsible for therapeutic failure in cases of acute otitis media in the Paris region.