FIG. 4.

Inhibition of intracellular multiplication of L. pneumophila by antibiotics. Live J774.1 cells were infected with L. pneumophila SG1 80-045 at 7.8 × 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. Bacterial growth after 72 h of incubation was quantified by counting the numbers of CFU on BCYE-α agar plates. Each column represents the mean ± SD for triplicate wells. ∗, significantly different from the control by Schaffe’s test (P < 0.01).