Isolation of nasopharyngeal beta-lactamase producing Haemophilus influenzae, in relation to antibiotic treatment of acute otitis media in infants.

This report is a compilation of clinical data involving the isolation of beta-lactamase producing H. influenzae made during a prospective study of 82 children suffering from different degrees of otitis media. Nineteen strains were isolated from the nasopharynx of 17 infants. Of these 63% were treated with amoxicillin because of acute otitis media within one month prior to isolation. These bacteria were found significantly more often in children who were heavily otitis prone than less so (p less than 0.01). beta-lactamase-producing H. influenzae were also found more often after treatments with amoxicillin than after penicillin-V (p less than 0.01). At the time of the next nasopharyngeal culture taken 5 to 69 days later, beta-lactamase-producing. H. influenzae could no longer be found, except in 2 cases. In the absence of antibiotics these strains seem to be replaced by other bacteria, such as Streptococcus pneumoniae and non-beta-lactamase H. influenzae.