Replied by Ted (Bangkok, Thailand)
Dear Louisa: Apple cider vinegar do not have the bacteria to go all the way to your urinary bladder. If it were, you should get stomach upsets, or intestinal cramps.
One way to get urinary tract infection is that you have not taken enough salts in your diet, such as sea salt, which can cause urinary tract infection whenever you drink too much water.
When drinking too much water, the amount of salts is reduced and the bacteria can invade the urinary bladder. Bacteria can't grow well in a salty environment, such as salted fish. Also newer bacteria on urinary bladder to date, I have found are now mure resistant to acid, such as strep bacteria.
So what the apple cider vinegar is doing is creating a favorable environment for acid loving bacteria. This does not happen often, but you can reverse the problem by adding heaping 1 teaspoon of sea salt to one half glass of water. The pain should reduce within 30 minutes if the treatment works. You need not wait weeks or days to know.