One thing to note is that you should see the sneezing stop or improve over the next few days to a week, depending on how long the breathing noises have been going. If you have been prescribed baytril, I used the `tea biscuit` method with the mice!
Take a rich tea biscuit or digestive. Wet it a little bit (but not soaked/mushy). Lie the biscuit on a saucer to go soft. Only offer a piece about 5mm in size. Dose the Baytril onto the broken edge of the biscuit and let it soak in. Offer the laced biscuit to the rat affected and he should swipe it! make sure the rat eats it all.
If you see an improvement (if your vet has given a high enough dose and duration) Baytril should be continued for at least two to three weeks. If it`s started and stopped, this can just build a resistance and allow the stronger bacteria to re-emerge as they will still linger if the drug is stopped prematurely. So if ratty seems better within four/five days, ring your vet for more Baytril because it proved the drug is having the desired effect. If after one week ratty is still much the same, then the drug may have to be changed to a Tetracycline. These can be given in tablet form and crushed up, but the rat forum people should be able to advise on the correct dosage.
Penicillin drugs will have no effect on mycoplasma as it is resistant. So drugs like Duphamox and Synulox won`t do anything. If you do need to treat with another drug, I would go the Tetracycline route.