Peanut butter (200 g) implicated in a 2008e2009 outbreak (Blakely, GA) was placed into a sterile 400 ml stomacher bag and warmed to 65 C in awater bath (Fisher Isotemp 220, Atlanta, GA). A 1 ml inoculum of each concentrated culture (approx 109e1010 cfu/ml) was added to the peanut butter and mixed in a stomacher (Seward 400, Bohemia,NY) for 2 min