I had a bunny who had re occurent snuffles....he had bayril...snuffles returned and then he had septrin. Snuffles returned so the vet decided to do a nasal swab while he was under GA and also they burred some small molar spurs. The swab results showed that the bacteria which was in large amounts in his nose actually needed to be treated with baytril. Strangely after that which was over a year ago he has not had snuffles since so whether it was due to the molar spurs or the antibiotic did actually kill the bacteria I'm not sure. I would try a long 21 day course of baytil first then if that doesn't work try another antibiotic. If it returns a third time I would ask for a nasal swab plus teeth check to be done under GA.