How Does A Puppy Get a Bladder Infection?

I kinda got a little ahead of things by posting the Santa Barbara trip. Maggie and I are still living in this small apartment ... she goes to "school", while Mom goes to work. We seem to have a schedule now but for the like of me, she is a little harder to "potty train" as my last Golden. I've been sleeping on the living room floor next to her crate for weeks now ... taking her out at night as soon as she stirs ... sometimes two to four times a night ... We go to the vet to get our second round of shots (or is it the third, I'm not sure) and I talked with the vet about a discharge I saw when she was peeing (I know, too much information) ... sure enough, Maggie has a bladder infection. The vet put her on Clavamox and I'm thinking okay, now at least we know what's been going on with her potty training ... I hope she didn't get it from the apartment complex, you know, there are other dogs there and her immune system isn't up to par yet ... poor thing ... at least now everything will be under control.