If e-coli is hazardous/toxic, how does it gain into everyone's intestines surrounded by the 1st place w/o making us sick?

My guess... there are several different strains of e-coli... some hardly cause stomach upset, others can gun down... and while it is beneficial in the intestines (the correct strain) it doesn't come across to play well surrounded by the stomach. The larger question is why it have been such a problem within recent years... and how does it get on vegetables? Using antibiotics indiscriminately surrounded by animals may be part of the problem... but it does give the impression of being like so masses different bio-threats have be occurring lately... and heaven forbid that you acquire sick and need to dance to the hospital where it is promising that you could pick up a staff infection... or, as has be in the report, even at other locations... like glorious schools.
Because the body is the greatest electrical device in the world. But gratitude to all the undereducated relatives working in food services that don't swab their hand and use matching gloves to scrub the toilets as they do dishes (true story). We find ourselves contaminated and sick from large amounts of e-coli.