Role of beta-lactamases in the response of pulmonary infections to amoxycillin/clavulanate.

Lung secretions from patients with bronchiectasis have been studied before and during treatment with amoxycillin/clavulanate (Augmentin 750 mg tds). beta-Lactamase activity was usually present in the sputum sol phase and originated from organisms not usually considered to be the major pathogen. The presence of beta-lactamase was related to inactivation of amoxycillin in the lung secretions. Extensive bacteriological investigation of the sputum before therapy showed several organisms to be present in each sample. Six of eight patients showed a good clinical and biochemical response to therapy with amoxycillin/clavulanate. This, however, could not be predicted or explained by the results of bacterial investigation although Haemophilus influenzae was eradicated in three of these responders. beta-Lactamase activity did not change during treatment, and this investigation thus failed to produce indirect evidence of penetration of clavulanate into the secretions.