Figure 3: Intracellular growth and cytotoxicity in THP-1 cell. (a) THP-1 cells were infected with L. pneumophila strains at MOI of 1 for 1 h. The infected cells were cultured in the presence of 50 μg/mL gentamicin. The infected cells were cultured for 1, 24, and 48 h and washed with PBS followed by lysis with cold distilled water. CFU were determined by serial dilution on CYET. (b) THP-1 cells were infected with L. pneumophila strains for 1 h. The infected cells were cultured in the presence of 50 μg/mL gentamicin for 1 h. After 24 or 48 h of incubation, the cells were washed and cultured in fresh medium. The supernatants of infected cells were collected, and LDH release was measured. All values represent the average and the standard deviation for three identical experiments. Statistically significant differences compared with the control are indicated by asterisks (, ).