Effect of prior antibiotic treatment on middle ear disease in children.

The effect of prior antibiotic treatment on the course of otitis media was assessed in a group of 62 children who experienced 83 episodes of ear infection during 3 years of observation. Bacterial quantitation in middle ear fluids demonstrated a significantly higher colony count in symptomatic children (3.9 x 10(4) +/- 12 bacteria per milliliter) compared to asymptomatic children (6.3 x 10(3) +/- 10 bacteria per milliliter; p = .05). Bacterial counts similarly tended to be higher in children with Streptococcus pneumoniae (4.0 x 10(6) +/- 16 bacteria per milliliter) and Hemophilus influenzae (2.0 x 10(6) +/- 16 bacteria per milliliter), who were more often symptomatic (73% and 55%, respectively, versus 38%) than children with Moraxella catarrhalis (7.9 x 10(3) +/- 2). Antibiotic therapy between 3 and 30 days prior to bacterial diagnosis was associated with a reduction in symptoms from 70% to 38% (p less than .025). However, prior treatment did not statistically reduce bacterial colony counts, although S pneumoniae decreased 90% in the previously treated group. Resistance to ampicillin occurred in 0% of S pneumoniae, 39% of nontypeable H influenzae, and 80% of M catarrhalis subjects without prior treatment and in 0%, 46%, and 100%, respectively, of subjects previously treated (p less than .025). These data suggest that prior treatment has a significant impact on the subsequent course of otitis media in children.