Forgive me if this has been asked before.

One of my kitties, Juliet, seems to be dealing with recurrent UTI's/kidney
infections.  I'm looking for *anything* that might help her.  Some history:

Juliet is a 7 year old spayed female.  She's an indoor kitty, and always has
been.   She has IBD, but is symptom free with Hill's Z/D.  All of my other
kitties are on Innova Low Calorie, and Juliet picks at that when her tummy
is doing well.  My kitties have a choice of litter--non-scented clumping,
worlds best, or non-clumping crystals blend.  Litter is changed/scooped
regularly.  Juliet looks very healthy.  She's a good weight for her size
(about 9 lbs) and her coat is fabulous.  She was tested for FeLV and FIV as
a kitten, and was negative then.  She sees the vet yearly for her vaccines.

Juliet was diagnosed with a bladder/kidney infection and treated about 2
months ago.  All my kitties went to the vet because someone was peeing
outside the litter box.  Juliet was NOT--but I figured I better take
everyone in, just to be sure.  Julie presented with lots of blood and rods.
She was treated with clavimox drops for 10 days.  About 5 days after the
antibiotics were finished, I took her in for a recheck, but she had no urine
in her bladder.  All was assumed fine.

Since my new baby kitten had an appointment for vaccines, I took Juliet back
for a UTI recheck at the same time.  Lo and behold, she's very positive for
infection again.  Lots of blood and cocci.  A radiograph shows no stones.
Temp is normal.  We drew blood for a CBC, kidney and thyroid panel--results
should be back tomorrow.  Right now, she's on 12.5 mg of Zeniquin once per
day, for 20 days (or as long as she can tolerate it.  Her IBD makes it
difficult to give antibiotics for extended periods of time.)

Does anyone have any ideas here?  I'm working closely with my vet, but I
want to do *everything* possible.  I'm concerned because it seems she
re-infected--first it was rods, now it's cocci.  She SEEMS healthy...I was
shocked when she was positive for infection the first time.

What else can I do to keep my poor kitty healthy?

Thanks!

Corey