TABLE 5.
Invasiveness and intracellular survival of invasive E. coli strainsa
| E. coli strain | Growth phase | No. of intracellular bacteria at 2 h | Intracellular survival at:
|
|
|---|---|---|---|---|
| 24 h | 48 h | |||
| HB101(pRI203) | Logarithmic | (1.8 ± 1.3) × 106 | (5.9 ± 3.3) × 103 | 0 |
| HB101(pRIEcSOD) | (2.3 ± 1.5) × 106 | (4.0 ± 1.7) × 105 | (1.5 ± 0.6) × 105 | |
| HB101(pRI203) | Stationary | (2.0 ± 0.6) × 105 | 0 | 0 |
| HB101(pRIEcSOD) | (9.2 ± 0.5) × 104 | (6.3 ± 0.6) × 104 | (1.0 ± 0.5) × 104 | |
| GC4468(pRI203) | Logarithmic | (1.3 ± 0.5) × 106 | (1.4 ± 0.7) × 104 | (1.0 ± 0.6) × 103 |
| GC4468(pRIEcSOD) | (2.1 ± 0.8) × 106 | (1.8 ± 0.6) × 106 | (3.6 ± 1.9) × 105 | |
| GC4468(pRI203) | Stationary | (3.0 ± 0.4) × 105 | (3.8 ± 0.6) × 104 | (1.0 ± 0.8) × 103 |
| GC4468(pRIEcSOD) | (2.8 ± 0.3) × 105 | (1.3 ± 0.9) × 105 | (1.2 ± 1.0) × 105 | |
| QC2725(pRI203) | Logarithmic | (1.0 ± 0.4) × 106 | (1.6 ± 0.5) × 104 | (2.0 ± 0.5) × 102 |
| QC2725(pRIEcSOD) | (1.1 ± 0.3) × 106 | (0.8 ± 0.4) × 106 | (3.6 ± 0.4) × 105 | |
| QC2725(pRI203) | Stationary | (3.3 ± 0.6) × 105 | (2.7 ± 0.6) × 104 | (2.0 ± 0.5) × 102 |
| QC2725(pRIEcSOD) | (5.1 ± 0.5) × 105 | (1.8 ± 0.7) × 105 | (1.6 ± 0.4) × 105 | |
a
Invasiveness (measured as the number of viable intracellular bacteria 2 h postinfection) and survival of E. coli strains within HeLa cells at 24 and 48 h postinfection were determined by infecting cell monolayers with bacteria (MOI, 100) in different growth phases, as described in Materials and Methods. Values are the means ± standard deviations of at least four independent experiments.