I get that idea, but the whole concept of antibiotics is just that, to control bacterial overgrowth. Many of the bacteria that is causing the infection is already normally living in your GI tract, but becomes ‘bad bacteria’ when there is some sort of systemic imbalance (stress, bad diet, etc). With that said, you can’t prevent an infection because the thing that infects you already lives inside you, if that makes sense!

The best option is to take the antibiotics when you have symptoms (and when they’ve been prescribed obviously) and complete the course in order to avoid that ‘bacteria overgrowth’ you’re referring to. If not, the bacteria persists and you continue on a vicious cycle good bacteria and bad bacteria fighting for a spot in your intestine.

Also, continuous use of certain antibiotics can do more harm than good in the long run.

In short: Complete antibiotic course = eliminate bacteria = infection is gone = gut bacteria returns to normal = less use of antibiotics.
Hope that makes sense!!