Phenoxymethylpenicillin and therapeutic failure in acute otitis media.

The aim of the present investigation was to determine to what extent beta-lactamase producing Haemophilus influenzae (H.i.) and Branhamella catarrhalis (B.c.) were isolated in cases of failure of treatment of acute otitis media (AOM) with phenoxymethylpenicillin. Among children with suspected therapeutic failure referred to an ENT specialist altogether 11, 15% of those referred, fulfilled the criteria of AOM. Three of them were on erythromycin, 1 on ampicillin and 7 on phenoxymethylpenicillin. In 5 of the children treated with phenoxymethylpenicillin H.i. was isolated from middle ear exudate and/or the nasopharynx. All H.i. isolates were non-capsulated and beta-lactamase negative. One beta-lactamase producing B.c. was isolated from the nasopharynx in a patient with pure culture of H.i. in the ear exudate. The present investigation did not support the suggestion that beta-lactamase producing H.i. or B.c. are major causative agents in therapeutic failures of AOM treated with phenoxymethylpenicillin and did not produce any evidence supporting a change from the recommended ampicillin esters/amoxycillin in therapeutic failures.