Activity of clarithromycin against murine listeriosis.

In-vitro clarithromycin was more active than erythromycin against Listeria monocytogenes. The antibacterial action was bacteristatic. In normal adult mice infected with a virulent strain of L. monocytogenes clarithromycin was also more active than erythromycin. A rapid decrease in viable count was obtained, which was not achieved with erythromycin. Early treatment resulted in a complete abrogation of an immune response to L. monocytogenes. In immunocompromised, congenitally athymic (nude) mice, only a moderate effect on the bacterial numbers was observed, indicating that even in vivo the activity of the macrolides is bacteristatic.