Trimethoprim-sulfamethoxazole in the treatment of otitis media secondary to ampicillin-resistant strains of Haemophilus influenzae.

Between August 1977 and January 1979, 16 children (7 males and 9 females) ranging in age from 5 to 38 months (mean age 18 months) were treated with trimethoprim-sulfamethoxazole (TMP-SMX) (40 mg/kg SMX per 24 hours) for otitis media caused by beta-lactamase strains of ampicillin-resistant Haemophilus influenzae. Fourteen patients had failed after antecedent ten-day courses of ampicillin (9 patients) or amoxicillin (5 patients) therapy. The remaining two patients received only five days of ampicillin before changing to TMP-SMX. Six of the isolates were nontypable, 3 were type B, 5 isolates were Haemophilus parainfluenzae, and 2 strains were unavailable for typing. Of 13 strains tested, 10 had a minimal inhibitory concentration (MIC) in excess of 3.12 microgram/ml of ampicillin; the remaining 3 had an MIC of < 3.12 microgram/ml. All 13 isolates were susceptible to 0.19 microgram/ml TMP-SMX. Five of 16 children were symptomatic (irritable; fever of > 38.2 C); within three days of starting TMP-SMX treatment, they became asymptomatic. Fifteen of 16 patients (93%) responded favorably after ten days of TMP-SMX. Only one patient had H influenzae resistant to ampicillin (12.5 microgram/ml) and sensitive to TMP-SMX (0.19 microgram/ml) isolated from the middle ear at the end of ten days of TMP-SMX. At the end of TMP-SMX therapy, middle ear effusions were noted in ten patients; the fluid was sterile in the four patients who had a second tympanocentesis. There were two recurrences within one month of TMP-SMX therapy. No adverse clinical reactions were noted.