Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Listeria generally effect infants or elder people, it can present in different way like fever, or may cause meningitis , though any infection can potentially cause low BP, but its not commonly found with listeria to cause low BP without other symptoms, so if you have no other symptoms of sepsis or bacteremia, I don t think its listeria , so we should see other causes of low BP, the most important here would be your medicine, so check it if its persistently low you can talk to your doc to reduce the dose of the drugs ,other causes are vomiting , diarrhea, or excessive sweating and a lot more. Hope I have answered your query. Let me know if I can assist you further.