If resistance to a specific antibiotic is not uniform in the population a mutation has spread one way or the other and which one is beneficial depends on the environment they subsequently encounter.
Now ask your friends to explain that to you sometime.
Well, I asked my neighbor about this, but he couldn't talk much as his allergies were flaring up. Besides, his family has had a lot heart disease problems and he is worried about himself.
Perhaps he's not as Human as I am: Or maybe, I'm not as Human as HE is!?
HMmmm...... maybe it's just his red haired children that are bugging him.........