Coliform bacteria are common contaminants of meats. In terms of food safety, why is it suggested to cook hamburgers medium-well to well-done, whereas
steaks can be cooked rare?
Coliform are rod-shaped gram-negative bacteria present in the intestines and feaces of may of the warm-blooded animals. They do not cause any illness in the animals. It acts as a pollution indicator and their presence is indicative of other disease-causing microbes. It contaminates the meat during slaughter.
Steak is obtained by slicing across the muscles. Beef, on the other hand, is ground and minced and is obtained from cattle. Hamburgers should be cooked to medium-well to well-done so that all the contaminants (coliform) if present gets killed. It is so because it is grounded and formed into a hamburger patty which enables bacteria to even reach into the center. The patty must be cooked from the center so that rise in temperature could kill the contaminants. While in the case of steak, cooking it "rare" is enough for killing or eliminating the contaminant because they may be present in the surface only (unless it gets penetrated into the muscles).