Infection assay.

<p>RAW264.7 cells were infected with Δ<i>ddp</i> mutant or wild type strain 2308 at a MOI 100∶1. A: The CFUs of total bacteria adherence to RAW264.7 cells. B: The CFUs of total bacteria invasion of RAW264.7 cells. C: Bacterial survival in RAW264.7 cells at 1 h, 12 h, 24 h, 36 h and 48 h p.i. All data are expressed as mean ± standard deviation and subjected to Student’s t-test, **, p≤0.01.