FIG. 5.

Inhibition by antibiotics of cytopathic effect of intracellular L. pneumophila. (a) Uninfected live J774.1 cells were treated with antibiotics. (b) Live J774.1 cells were infected with L. pneumophila SG1 80-045 at 8 × 10⁵ CFU/well (20 times the CPED₅₀) for 12 h. After the extracellular bacteria were washed out, antibiotics were added to the wells at the indicated concentrations. After 72 h of culture the remaining J774.1 cells were stained with MTT and the optical density (OD) of the purple formazan product was quantified at 550 nm. Each column represents the mean ± SD for quadruplicate wells.