bladder infections and food

Question
I have a question regarding quality pet food and bladder infections / UTIs.  I have a 4.5 month old labrador puppy and have been feeding her Blue Buffalo life source puppy food since I got her (@ 8 weeks).  we have been incredibly pleased with her and the food.

However, upon returning from a weekend trip to the beach, the following day she urinated in her cage numerous times, in the house and outside she appeared to urinate every 10-15 minutes, sometimes just a few drops.  (Prior to this, she had not urinated in the house or cage for a month or so).

After taking her to the vet, hew measured her pH, etc. with a test strip which revealed a high ph = 8.0 and no blood or bacteria.  However, after a proper lab analysis, the pH = 7.2, bacteria was found and her white blood cell count was up leading up to some sort of bladder infection.  The vets first guess was that, (since the pH was high and there was no evidence of bacteria in the test strip) that her food was beginning to cause high pH and some bladder iritation and he recommended I switch foods to Science diet puppy.  Since the lab results came back, he feels there is definitely some infection in her bladder and got her on a 10 day antibiotic pill and still wants me to change the food.  He speculates that the food is still the problem and doubts that she picked up something in the water the previous day or two before the symptoms started to arise.

So my (long winded) question is.....is this a common occurence with the higher-end foods?  I read another question that points to the vegetables in the food leading to a high pH.  Do you think that since Blue Buffalo uses fresh vegetables in thier food that after a couple months of feeding that could have irritated her bladder?  Should this have happened earlier or would it take a couple months for it to eventually manifest into a bladder infection?  Or do you think this may be from something she picked up in the water the previous day?  

Please know, my primary concern is my dog and I want to find her the best food and give her what will nourish her the best.  I chose blue buffalo b/c it does not use corn as the first ingredient and provides (in excess maybe) all the "standard" nutirtional components.

Answer
While I agree that it can be food related, imo to switch from BB to SD is going from the frying pan into the fire. If you feel the need to change dog foods, I would choose instead a low ash, grain free food. Definitely not Hills.
Blue Buffalo is a GOOD dog food and chances are it is not related. However you can find foods with higher water and lower ash content.
http://www.dogfoodproject.com/index.php?page=grain_free
Here's a website with a breakdown of quite a few foods, ingredients listed, protein and fat levels, water and ash levels
You want low ash, no grain, high water.
Make SURE she goes to potty VERY often, at LEAST once every two hours. Force fluids, unsalted chicken broth etc, anything and everything she will drink.
Exercise is crucial and lots of it
Veggies have nothing to do with it and are wonderful for her. I honestly DOUBT it's the food.
However it can be caused by allergies, therefore the fewer ingredients you have in her food, the better.
Good luck
Cindi
PS I hear of MUCH fewer UTI's in dogs on high end dog food than the opposite