Branhamella catarrhalis as an indirect pathogen.

In 7 patients with bronchopulmonary infections, treatment with penicillin antibiotics failed to eradicate Haemophilus influenzae or Streptococcus pneumoniae which were sensitive to the antibiotic used. The sputum of these patients contained both the pathogen and beta-lactamase-producing Branhamella catarrhalis. No antibacterial activity was detectable in sputum samples obtained from patients receiving a penicillin antibiotic. This suggests that B. catarrhalis can act as an indirect pathogen, protecting accompanying pathogens from antibiotics by producing an antibiotic-destroying enzyme.