Your vet certainly is on top of things with Luna. If the treatment for e-coli isnt to harsh/harmful to body organs than I would try that route. Yes, antibotics clear up bacteria, but there is always a source to that bacteria. It appears the source of all the bacteria problems remains a mystery with Luna, that would be the frustrating part. Would your vet consider doing blood workups on a more regular basis to compare results? Maybe a pattern might develope that would make things more clear.