Table 1.

Association to and invasion of HeLa cells by BCYE-grown and HeLa cell-grown (mature intracellular bacteria) L. pneumophila 2064

StrainViable cell counts (CFU/monolayer)a
Expt 1,b associationExpt 2c
AssociationInvasion
BCYE grown(1.5 ± 0.65) × 103 (1.2 ± 0.4) × 104 5.0 × 103
HeLa cell grown(1.6 ± 0.53) × 104 (2.0 ± 0.3) × 106 (4.2 ± 2.5) × 105
  • a Association refers to adherent and intracellular bacteria; invasion refers exclusively to bacteria that survived treatment with gentamicin (100 μg/ml) and were assumed to be intracellular.

  • b Invasion assay run at a bacterium-to-HeLa cell ratio of 10:1. Inoculum was ∼106 bacteria on a monolayer of ∼105 HeLa cells. Results are shown as mean ± standard deviation from a single experiment run in duplicate.

  • c Invasion assay run at a bacterium-to-HeLa cell ratio of 20:1. Inoculum was ∼107 bacteria on a monolayer of ∼5 × 105 HeLa cells. Results are shown as mean ± standard deviation from a single experiment run in duplicate, except for the invasion sample from BCYE-grown bacteria, which represents a single determination.