I ate food that was recalled due to listeria. how soon would the bacteria show up on a blood test? possibly pregnant.

Listeria outbreak: It is quite unlikely for Listeria to show up in the blood. Most commonly a "GI illness" is what occurs - such as nausea/vomiting or diarrhea. For those who's immune system is weak - including older age, cancer, HIV/AIDs, or even pregnancy - then it's important to check professionally with a doctor for any fevers or other signs of serious illness. Listeria, when it attacks, is a serious illness.