Culturing and Inactivating Bacterial Strains

Lactobacillus plantarum NCIMB 8826 (ATCC BAA-793) and Lactobacillus reuteri F275 (ATCC 23272) were cultured overnight at 37°C in Difco Lactobacilli MRS Broth (BD Biosciences, Sparks, MD). Listeria innocua Seeliger (ATCC BAA-680) cultures were generated by overnight growth at 37°C in Sheep Brain Heart infusion medium (Thomas Scientific). Serial dilutions were plated and counted to correlate the number of colony-forming units per milliliter (cfu/mL) with the optical density at 600 nm (OD₆₀₀). Bacterial cultures were harvested by centrifugation (5 min, 1500 rpm), washed with phosphate-buffered saline (PBS), and suspended in PBS with 1% bovine serum albumin (BSA) just prior to inoculation. Inactivated bacteria were prepared by washing in PBS and heating to 95°C for 30 min prior washing in PBS and resuspension in PBS with 1% BSA; inactivation was confirmed by overnight culture in appropriate culture broths.