ROD21 excision frequency increases when <i>S.</i> Enteritidis infects phagocytic cells.

<p>Bone marrow-derived DCs (<b>A</b>) and J774.3 macrophages (<b>B</b>) were infected with <i>S.</i> Enteritidis (MOI equal to 25). After 2, 18 and 24 h post infection (hpi) intracellular bacteria were recovered and the copy number of the <i>attB</i> sequence generated by type 1 excision was detected by quantitative PCR, using as template the genomic DNA obtained from intracellular bacteria. Frequency of excision is expressed as the ratio between the copy number of the <i>attB-1</i> sequence determined for intracellular and extracellular bacteria. The DNA amount was normalized by calculating the copy number of the <i>rpoD</i> gene. Data shown in graphs are average values of at least three independent experiments. The amount of intracellular bacteria recovered after 2, 18 and 24 hpi from DCs (<b>C</b>) and J774.3 (<b>D</b>) was determined by lysing either 1,000 DCs or 100 J774.3 cells with PBS-triton X100 (0.1%) and seeding the lysates in LB plates. Data shown are the average of at least 3 independent experiments.</p>