Bactericidal effects of amoxycillin/clavulanic acid against a Legionella pneumophila pneumonia in the weanling rat.

Amoxycillin/clavulanic acid and clavulanic acid have been previously reported to demonstrate bactericidal activity in tissue culture studies against intracellular Legionella pneumophila. A rat model of legionellosis was therefore developed for the purpose of assessing the efficacy of these agents against L. pneumophila in vivo. Therapy by the subcutaneous route was started 12 h after infection when the majority of the bacteria observed in lavage fluid were residing in alveolar macrophages. Treatment with amoxycillin was ineffective in reducing the bacterial counts of L. pneumophila in lung homogenates whereas amoxycillin/clavulanic acid displayed bactericidal effects of the same order as the control antibiotic, erythromycin. Further in-vivo studies are planned to assess the clinical relevance of these findings.