The effects of treatment of acute otitis media with a low dose vs a high dose of amoxicillin on the nasopharyngeal flora.

OBJECTIVE To compare the effects on the nasopharyngeal flora of therapy of acute otitis media in children with either a low dose or a high dose of amoxicillin. DESIGN Retrospective study. PATIENTS Of 50 children diagnosed as having acute otitis media, 25 received a low dose of amoxicillin (45 mg/kg/d) (group 1) and 25 received a high dose of amoxicillin (90 mg/kg/d) (group 2) for 10 days, and both groups were evaluated. INTERVENTION Antimicrobial treatment. RESULTS Before therapy, potential pathogens (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Staphylococcus aureus) were isolated from the nasopharynx of 15 children in group 1 (60%) and 13 in group 2 (52%). The number of penicillin-susceptible isolates was equally reduced after both therapies. However, an increase was noted in the recovery of S aureus only in group 2 (from 2 to 6 organisms). A greater eradication rate of interfering organisms following therapy was noted in group 2 (from 86 to 36) than in group 1 (from 92 to 60) (P < .001). These organisms include alpha-hemolytic streptococci, and Peptostreptococcus and Prevotella species. CONCLUSIONS The oral flora at the end of therapy with a high dose of amoxicillin is more depleted of organisms with interfering capability than following treatment with a low dose of amoxicillin. These changes may contribute to the greater recovery rate of patients infected with S aureus who received a high dose of amoxicillin.