Potential significance of colonization with beta-lactamase-producingHaemophilus parainfluenzae in children

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Abstract
Recent surveys in Vancouver showed most healthy children were colonized withβ-lactamaseproducingHaemophilus parainfluenzae. Such organisms might alter the effects of penicillins on throat bacteria by local inactivation. To test this hypothesis in vitro, three isolates ofβ-lactamaseproducingHaemophilus parainfluenzae were each mixed on a membrane with ampicillin-sensitive strains ofHaemophilus influenzae type b or group AStreptococcus pyogenes and exposed to ampicillin. When tested alone, susceptible strains were rapidly killed but when tested together with aβ-lactamase producer, they were protected, indicating efficient ampicillin degradation byHaemophilus parainfluenzae strains. If similar interactions occur in vivo, the effects ofβ-lactams on throat bacteria could be significantly altered in the presence ofβ-lactamase-producingHaemophilus parainfluenzae.