Trim the lettuce of pre-cut ends, tears and bruises, then immerse in a cold water bath with a food grade surfactant (made for washing fruits and vegetables in) and agitate gently for a dozen or so seconds, then rinse under cold running water. Dress with a vinagrette or good italian dressing liberally, which should have a similar disinfecting effect as vinegar in the rinse water.

I am still an advocate of irradiating fresh food. It does nothing to the taste, texture, or quality of the food, and doesn't make it radioactive either, but can wholly eliminate any remaining pathogens.