I have never worked in a processing facility either but I watch those how it is done things on the Science channel and I’ve never seen one that they don’t thoroughly wash anything that they are processing.
As far as E. Coli and Salmonella the obvious answer (at least for me) is irradiation.
Five hundred Rads of gamma radiation and you need not worry about any kind of biological contamination causing any kind of sickness. And there is the added benefit that the food will remain edible for many times longer.
Personally I would pay a couple of extra bucks for irradiated food (especially meat).
That’s why I was thinking of the processing plant rather then the farm. They could add it after it has been inspected and washed.