Bacterial viability of intracellular C. jejuni.

Islands of polarized Caco-2 cells were infected with C. jejuni for 5 h in Hepes buffer, washed, incubated (3 h) with gentamicin (250 ìg/ml) in DMEM, washed again, and incubated for an additional 42 h in DMEM plus 10% FCS with a low dose of gentamicin (50 ìg/ml). At the indicated times, samples were prepared for bacterial viability assay. (A) Gentamicin killing assay showing the bacterial recovery of intracellular C. jejuni strains 108 containing pMA5-metK-luc (white and light grey bars) and 81–176 containing pMA5-metK-luc (dark grey and black bars) from Caco-2 cells at the indicated duration of infection. CFU were enumerated after 48 h of recovery on agar plates in a 0.2% oxygen (white and dark grey bars) and 5% oxygen (light grey and black bars) environment and indicated as CFU per well. (B) Bacterial viability as measured by bacterial luciferase reporter assay at the indicated time points. Values for results presented in (A) and (B) are the mean ± SEM of at 3 independent experiments in performed in duplicate.