The temperature at which bacteria in meat dies when cooking is 120 F.
However some types of bacteria may still live even at 120 F so for some meat you need to cook to an internal temperature of 165 F which ensures the bacteria is killed off.
I always will cook any types of meat until the internal temperatures reaches at least 165 F to make sure that all bacteria that could be in the meat is killed.
I don't want to risk getting sick and cooking the meat to 165 F internal temperature ensures the meat is fully cooked as well.
Some people like their meat medium rare but I like all my meats to be well done.
But if you do cook most meat to at least 120 F most of the bacteria is killed off.