E-coli in meat is easy to kill, and is only a danger when the meat is raw or undercooked. Well-cooked (which all ground meat should be these days) = no problem. The days of rare hamburgers and steak tartare are long gone, due to the low standards of the meat-packing facilities and the ineptness (is that a real word?) of the USDA. On chunks of meat, the danger is from the surface, not the interior (excepting poultry).
Safe temperatures for meat:
Ground beef, pork, veal, lamb: 160F
Ground turkey or chicken: 165F
Fresh beef, veal, lamb (steaks, roasts, chops): 140F
Poultry (whole, pieces, roasts, stuffed): 165F
Pork & ham: 145F
https://www.foodsafety.gov/keep/charts/mintemp.html
You will have noticed that the highest temps go along with the highest risk of contamination.
An all-metal meat thermometer (~$5) is inserted into the thickest part of the meat before you cook it, and only removed when the meat is done. Aim the dial where you can see it. Ground meat (hamburgers) are done when none of the interior meat is pink. Photo:
https://images.samsclubresources.com/is/image/samsclub/0007013103231_A?$img_size_380x380$
An instant thermometer ($80+-) has plastic on it, and is only used momentarily when you're checking the temp, NEVER left in the meat. Photo:
https://images-na.ssl-images-amazon.com/images/I/81vyFmAXwQL._SL1500_.jpg