FIG 5.

c-di-AMP induces ifn-β expression and promotes S. aureus intracellular survival in human MDMs. (A) Human MDMs were treated with c-di-AMP (0.01 to 10 μM) for 3 h, whereupon RNA was isolated and analyzed for changes in ifn-β expression by qRT-PCR. Gene expression levels were normalized to the housekeeping gene gapdh and are presented as the fold induction (2^−ΔΔCT) value relative to untreated MDMs. (B) MDMs were pretreated with c-di-AMP (0.01 to 1.0 μM) for 1 h, whereupon cells were incubated with live S. aureus at an MOI of 5 for 2 h and subjected to a gentamicin protection assay, in which MDMs were lysed 24 h later to quantify intracellular bacteria. Statistical analysis was performed using a one-way ANOVA method with Tukey post hoc analysis. *, P < 0.05.