Prophylaxis with amoxicillin or sulfisoxazole for otitis media: effect on the recovery of penicillin-resistant bacteria from children.

The rate of recovery of oropharyngeal penicillin-resistant Streptococcus pneumoniae and aerobic and anaerobic beta-lactamase-producing bacteria (BLPB) from children who received a 4- to 6-month course of prophylaxis with amoxicillin or sulfisoxazole for otitis media was investigated monthly over 9 months. The BLPB recovered were Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, pigmented Prevotella species, and Fusobacterium species. The recovery rate for all penicillin-resistant S. pneumoniae isolates and BLPB increased only after administration of amoxicillin. Before amoxicillin was administered, six BLPB isolates were recovered from four of the children who were to be given this drug (20%). The number of BLPB recovered increased gradually until all of these patients were found to be colonized with BLPB; five (25%) of these patients were found to be colonized with penicillin-resistant S. pneumoniae after 5 months of prophylaxis. Three to five months after amoxicillin prophylaxis was discontinued, the number of BLPB recovered gradually declined; only three children (15%) remained colonized with BLPB, and none remained colonized with penicillin-resistant S. pneumoniae. These data illustrate that amoxicillin prophylaxis induces an increase in the number of penicillin-resistant bacteria in the oropharynx.