Listeria were grown overnight in BHI at 37uC and cultures were centrifuged at 8000 g for 5 min. Bacterial pellets were resuspended in 75 mg/mL lysozyme and incubated at 37uC for 1 h. DNA was then extracted using the DNeasy blood and tissue kit (Qiagen) and quantified by spectrophotometry (Nanodrop). For transfection assays, THP-1 macrophages were transfected with 200 ng/mL DNA with 2% lipofectamine 2000 (Invitrogen) and incubated for 24 h. Following incubation, supernatants were collected for IFN-b analysis. For pretreatment of DNA with DNase, DNase was added at final concentration of 100 mg/mL for 45 min at 37uC.