Augmentin is Amoxicillin + Clavulanic Acid.

When I was treated for Enterococcus faecalis in my prostate years ago, the urologist I saw prescribed Augmentin and said the clavulanic acid is needed to get the amoxicillin across the prostate since it's a tricky barrier to penetrate. It either didn't work or I kept getting reinfected... until I finally took Levaquin (which left me with lots of other problems).

I've unfortunately got Enterococcus again. A month of Augmentin didn't work late last year or I got reinfected, so an infectious disease doctor has prescribed a much higher dose of just Amoxicillin (1000mg 3x a day, for 2-3 months), WITHOUT Clavulanic Acid. He says the reason they use clavulanic acid is to prevent gram negative bacteria enzymes from breaking down the amoxicillin and that this is a non-issue for me. He doesn't want me to take amoxi + clavulanic because he says it could increase side effects.

So... why did the urologist say clavulanic acid is necessary to get through the prostate barrier if it's not true? If it IS true, can someone point me to a credible website that states it?

I'd like to have a full understanding of what's going on here before going on more antibiotics as whatever I use has to work this time.
Please help. Thanks!