Hi Rene,
That's a very succinct but helpful summary you've presented. I have two ideas for you, which can be used together, and both of which would be expected to help the dog by rallying the dog's immune system, while promoting better urinary tract circulation. That might make any antibiotics being used more effective, or might even suffice on their own.
First off, I wonder about Blood stasis arising from the refractory UTI. Chronic inflammation in any organ is attended by very poor and disorganized circulation. In Chinese medicine they acknolwedged that by calling it Blood stasis. So one option is a Blood mover for the region. An example, and there are many that might work, is Shao Fu Zhu Yu Tang, if the dog is on the decrepit and chilly side. This is an easy formula to access, through us or someone else.
The second thing to consider is Ba Wei Di Huang Wan (Rehmannia Eight Combination). It provides general renal and geriatric support, whether from a Chinese or western point of view. The version with Cinnamon and Aconite is fine, especially if you're using the SFZYT simultaneously. If not, you could contemplate the version where Astragalus (Huang Qi - an immune stimulant) and Schizandra (Wu Wei Zi - for incontinence) are added. Another Kidney tonic worthy of consideration is You Gui Wan, but Rehmannia Eight is safer if you're just plunging into a case.
Points that may help: BL 27, BL 28, KI 3, BL 23, Bl 17, BL 40, ST 36 or 37.
Hope that gets you somewhere. We always hand out a lot of advice here and seldom here how it works out. Feel free to let us know,
Steve