Men, and the sensitive, look away.
I used to get killer UTI's, used to get them all the time. Then I was given two really good pieces of advice by a wonderful lady Gyn. She wasn't my regular Dr; but after a particular nasty and hard to kill UTI I had a test run that "typed" the bugs causing the UTI, and she was the ER doc that read the test. Turns out it was a rare bug, and it was her belief that it had colonized either the skin of my or DH's body, especially The Area In Question. Happens a lot, apparently, kind of like how staph bugs live on your skin.
The bacteria live there in that region happily, until the actions of intimate relations force them up into the urinary tract. They then begin to migrate upwards and multiply and cause UTIs and kidney infections.
Anyhow, she said always always ALWAYS urinate after intimate relations, more than once if possible. This will wash the bacteria back down and out again. Also, a quick swipe before and after The Deed with an antibacterial wipe in the general region may help too - cut down on the bacteria that are living there waiting to be banged around. NEVER let yourself fall asleep without a trip to the potty afterwards.
I know, to this day, if I fall asleep after enjoying marital relations without a visit to the potty, I will be writhing on the floor, peeing blood, in agony, within 24 hours.