It isn't just that we are immune to bacteria, etc. living in and on us. Because not all little critters are harmful to other living things anyway. More importantly, we couldn't survive without them. We couldn't efficiently digest our food, we would have a heck of a time keeping our skin clean enough and other little things like that (ear wax is kept in check by bacteria that eat it, for instance).
A recent medical breakthrough is the fecal transplant. People who are not able to digest food well oft times have problems because they don't have enough bacteria in their system. To fix it, doctors take fecal matter (yes, I know this is gross) from a person with a healthy digestive system and implant it into the guts of the sick patients. In most cases, they start getting better very quickly.
People with not enough bacteria = sick. People with lots of it = healthy. Go figure.
Some pundits have suggested that we humans evolved to transport around our beneficial bacteria from place to place. But obviously we evolved together. And hence we are mutually beneficial.
The sharp rise in the use of antibacterial products has harmed our personal ecosystems. People who use such products are helping to speed up the evolution of some harmful bacteria, and hospitals are now having to deal with new pathogens that are now immune to simple antibacterial medical treatments. Evolution in action, folks.
Plus, no study that I can find shows that the use of antibacterial soaps helps one iota. Some studies, however, suggest that when antibacterial products are used by people who already have asthma or diabetes, those people get infectious diseases more often than they would if they used just plain soap. Go figure.
So, they need us, we need them. If a god or gods were involved, they sure were real smart about including necessary non-human critters in our makeup to make us healthier. But if they knew that much about bacteria, why then are we having to deal with staph infections, strep infections, gonorreha, salmonella, e. coli and other nasty things? If the dude/dudette/gods of any gender really loved us, and they knew enough to provide us with nice little single celled organisms that love and consume our waste material, why did they also toss in icky things that kill/maim/disgust us? Not too nice, if you ask me.