Can you tell me how come you can get e/coli from lettuce, green onions ect should be washed before you eat but, mushrooms?

They can all have it: Any produce grown or processed near livestock or meat products may be contaminated by e. Coli. In general, you should wash your produce carefully and consider steaming, boiling or sauteing your vegetables, if you are worried about getting sick. Make sure you cut vegetables first before cutting meat or use separate cutting boards or wash board in hot, soapy water after cutting meat.