>> if antibiotic resistant bacteria survive, why would finishing the course of antibiotics make a difference?
I can only speculate, but here's how I imagine it.
Your body can kill a certain number of bacteria on its own. Antibiotics help reduce the infection to the point where your body can do the rest.
If the resistant bacteria are a small minority, taking antibiotics long enough to kill most of the non-resistant ones will let your body kill the remaining resistant ones.
If you stop too early, the battle tide has not yet turned. Instead, by killing, say, half the non-resistant ones, you've made the resistant ones a larger proportion of the whole infection. Then both groups continue to multiply.
If you repeat this several times, starting and stopping the antibiotics depending on how you feel, the resistant bacteria could go from being 1% of your infection to 50%.
I can only speculate, but here's how I imagine it.
Your body can kill a certain number of bacteria on its own. Antibiotics help reduce the infection to the point where your body can do the rest.
If the resistant bacteria are a small minority, taking antibiotics long enough to kill most of the non-resistant ones will let your body kill the remaining resistant ones.
If you stop too early, the battle tide has not yet turned. Instead, by killing, say, half the non-resistant ones, you've made the resistant ones a larger proportion of the whole infection. Then both groups continue to multiply.
If you repeat this several times, starting and stopping the antibiotics depending on how you feel, the resistant bacteria could go from being 1% of your infection to 50%.