The bacteriology of recurrent otitis media and the effect of sulfisoxazole chemoprophylaxis.

Middle ear effusion specimens were obtained from 31 children with recurrent episodes of acute otitis media. Of 75 total specimens 28 were obtained from children during chemoprophylaxis with sulfisoxazole. A single organism was isolated in 65 of 70 instances. Beta-lactamase was produced from Gram-negative organisms in 11 instances, and penicillin resistance from Streptococcus pneumoniae occurred in one instance. Haemophilus influenzae predominated during prophylaxis; S. pneumoniae predominated without it. Serotyping and biotyping were performed on 28 isolates from 8 children with consecutive episodes. In 17 instances the infecting organism was the same species but seven of these strains differed in serotype or biotype. The average number of weeks between onset of recurrence in children with homologous strains was shorter (2.6 weeks) than in the children from whom heterologous strains were found (5.7 weeks). Three media were evaluated for efficacy in 32 episodes, and direct plating resulted in the highest rate of recovery.