Interaction of <i>L. pneumophila</i> serogroup 1 strains with host cells.

<p>One strain from patient (ID119442), one strain from the outbreak source's cooling tower (ID120292), and three from environment (other that the outbreak source) (ID120145, ID120086 and ID120329) were tested. JR32 and an isogenic <i>dotA</i> deficient strain was used as a negative control for intracellular multiplication (ICM) and cytotoxicity. A) ICM in infected human macrophages (THP-1) and <i>Acanthamoeba castellanii</i> (AC). The data represent the ratio between the CFU at time 72 h and the CFU at time 0. Star represent difference statistically significant (<i>P</i><0.01). B) Evaluation of cytotoxicity on the viability of THP-1 cells after infection for 5 days with the MTT assay. The star represents difference statistically significant (<i>P</i><0.01). Error bars represent standard deviations derived from three independent experiments.