Quick answer: Food enters the human digestive system through the mouth before then moving through the pharynx, esophagus, stomach, intestines, rectum and anus.
The population size of a predator species is directly controlled by the population size of it's prey. If the predator has no prey the population size will go down because they have no food.
Overuse of antibiotics is causing this resistance, we can let our bodies fight off bacterial infections naturally, stop the overuse of antibacterial soaps and cleansers, let our bodies build up resistance to these bacterias naturally through natural exposure.