As you know, PA is EVERYWHERE! It's unavoidable. We can take precautions by washing our hands, keeping our homes as clean as possible, staying away from known contaminated areas, but it is still every where. Once PA gets into the CF lungs, it can be eradicated, but it can also grow back. Our daughter cultured PA for the first time when she was 6-years-old, right about the same time we started the GSH. But, a friend of ours has a daughter with CF that cultured PA at age 5 and has never touched GSH. It is frustrating, I agree, that although we give our kids GSH in the hopes that it will prevent PA from growing, PA is a very strong bacteria that is very difficult to manage. Don't blame yourself for it and I wouldn't be too quick to say that the GSH has anything to do with it. If you compare those with PA that use GSH to those with PA that don't, I think you will see that they are pretty similar. I do think GSH probably helps the lungs, but I have no evidence of that. We stopped oral GSH b/c my daughter was having major digestive issues and we do not know what the root of it was. But, we still do the inhaled and other than PA, she has no problems. Her weight is good, her lungs are fabulous...but she does still grow PA. I hope this helps. Without Tobi, PA would grow out of control, so we are happy to use it. I do have a friend that has been able to eradicate PA from his daughter's lungs for a good 3 years now. He swears by bleaching the drains, washing hands, bathing his daughter immediately after school, installing UV lights onto the air conditioner coil, UV lights on the water sources, no plants, no pets. He gives his daughter Zithromax, NAC (600 mg a day), vitamins, Creon and she is healthy as a horse. Good Luck.