urinary tract infection or contagious disease?

Question
QUESTION: hi sandra, i recently lost one of my boys, loki, to what i thought was a urinary tract infection. he was quite poorly in the evening and peeing blood so i put him on baytryl and decided to take him to the vet's in the morning. however, unfortunately he did not make it through the night and had already gone when i woke up early in the morning. having had previous experience with UTIs i did not expect him to go downhill so quickly. now, a week later another boy, seth, was exhibiting the sam symptoms and deteriorating very quickly. luckily i got him to the vet's in time and he was saved by a steroid injection and a high dose of baytryl which was injected and which i am now still administering orally. another week later, horus, seth's brother, was showing the same symptoms. again, he was saved by a steroid injection and baytryl which he is still receiving orally at the moment. both seth and horus are now symptom free and seem perfectly normal.
i am now wondering whether this is something contagious as it seems too much of a coincidence for it to just be a succession of random urinary problems. both my vets are completely baffled and so are all the other rat owners i know, even though they have years and years of experience. i have come across UTIs before but never anything as detrimental as this. i have 6 other boys living in the same cage. one of which is only 12 weeks old so i am of course very very concerned. any advice would be much appreciated!!!!
best wishes,
nicole (portsmouth, uk)

ANSWER: I am really sorry about Loki. I just lost my boy a week ago. Its nice to think that maybe my Smudge boy and your Loki are playing together !!

Now about this  mystery illness:

Was a urine culture done and if so, what bacteria was found?

If it is a serious bacteria that they could be contracting from the cage that is causing this, it would make sense that it is contagious among the other rats,  
It could absolutely be caused from an outside source, which is why I needed to know what the lab results were.  Please let me know.

---------- FOLLOW-UP ----------

QUESTION: thank you very much for your prompt reply! and so sorry to hear about smudge!!!

no urine culture has been done so far i'm afraid. when my vet pulled up some of seth's urine that he had very conveniently left in a puddle in his carrier, he said that there was too much blood in it to get anything out of it. i know that blood in urine always looks a lot more than it actually is but this was not even remotely seethrough anymore. just dark red like blood coming directly from a cut. however, if any of the others should be getting this as well i will be asking him again as it is really really important to me to get to the bottom of this. i clean the shelves in the cage twice daily and give the whole thing a good scrub once a week (including washing all hammocks and replacing with clean ones) but is there anything in particular that i could use to disinfect the cage (and something that is available in the uk)? i am all for using only natural products around the rats so would vinegar do the trick or is this only good for keeping down smells?
could it have been something brought in via their food or bedding? i have them on the shunamite diet and was using alpha herbal rabbit food as a base for the mix (which i have now replaced as the quality was just deteriorating with every sack) and burns dog kibble (now i am using vitalin). as bedding i am using cardboard squares (also known as ecopet bed). mysterious though why it only seems to be one at a time and with a week in between. i am going to see my preferred vet tomorrow and will be asking him a few questions as i only saw his colleague with horus on saturday.

thank you again for your help! i shall be trying to get as much info as i can on this.

best,
nicole

Answer
I am a bit confused as to why the vet said there was too much blood to do a urine culture.  Blood or not, if there is bacteria in the urine, it would grow.  However, getting a sample from a puddle in the carrier is not really ideal either. It can give all sorts of false readings if it picks up other microorganisms from another source.  This will simply confuse things and it would be too hard to pin point the bacteria that is causing infection to the point of irritation that is causing broken blood vessels etc... if that is what we are dealing with at all.  Again, it could be urinary stones or crystals.