Bacterial interference in the nasopharynx following antimicrobial therapy of acute otitis media.

The effect on the nasopharyngeal bacterial flora of therapy for 10 days with co-amoxiclav or cefprozil was studied in 50 children with acute otitis media. Before therapy, potential pathogens (Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis) were isolated in 14 (56%) of those treated with co-amoxiclav and 15 (60%) of those treated with cefprozil. Following therapy, the reduction in the number of these pathogens was the same in the two groups. However, differences between the groups were noted in the recovery of organisms with interfering capability, namely alpha-haemolytic streptococci, Peptostreptococcus anaerobius and Prevotella melaninogenica. Fifty interfering organisms were recovered from each group before therapy. After therapy with co-amoxiclav or cefprozil their number declined to 11 and 42, respectively (P< 0.001).