So what can the salad eater do to be safe? Some pathogens can't be washed off. Others can if you scrub, but not if you rinse. If you buy the whole head, pathogens can hide in the core. And if you buy pre-cut bagged salad, how can you wash that? What if you drench the salad in vinegar before eating it, will that kill E. coli O157:H7?
What I've heard (and I'm only citing unverified word of mouth) is that E.Coli is within the leaf itself, it comes from the water it used. You cannot wash it off or clean it. An infected head of lettuce is garbage.
https://www.tandfonline.com/doi/full/10.1080/011406710037678...
Skip down to the section on "Internalization of bacteria into deeper plant tissues"