Mycoplasma is so common in chickens and really makes no difference unless you have a confined flock and need maximum weight gain in the shortest time possible.I can tell you that even buying from reputable isn't a solid guarantee, unfortunately. I don't cull anything with the sniffles nor have I ever had any die from it. Bought from a few reputable breeders and all of a sudden my flock had it. Never had huge issues with it and it always clears up and only a few birds get it at a time so I am not so threatened by it anymore like I use to.
Only 15 states care or test for it with a NPIP flock even...and I know some of them are looking at dropping it.
Tweety birds and waterfowl can spread it..