Our son cultured pseudomonas when he was around 14 months. It made our hearts skip a beat, especially after a rough first year. We cried and were very worried.
He had a round of inhaled antibiotics (Tobramiacin, sorry about spelling) twice daily, nebulized, for 2 weeks. He is now 22 months and has not cultured it since! Most clinics are just aggressive with it the first time they culture because they don't want to give it an opportunity to set up shop. Some DR just do the inhaled as it doesn't aggravate the digestive system, some do a combo of inhaled and oral, others go right to IV. It is your choice based on what you think would be best for your baby. We went with inhaled only since it felt to us it was going directly to the site so to speak (and he wasn't showing any signs of illness) and it wouldn't mess with his GI tract. If you do oral, I would highly recommend adding acidophilus (lactobacillus) to his vitamin reginmen. It helps protect the intestinal tract and build up the "good" bacteria in the gut (flora). Culturelle is the brand we've been using since he was 4 months old and you can find it at most pharmacies or health food stores. We put it on a spoon with applesauce as if your giving enzymes, now we give it mixed in with his vitamins daily to help keep his gut healthy and lower inflamation. I believe we did 1 cap daily by the time he was 6 months old.
Hope this helps and just know that it doesn't necessarily mean any thing negative to his future. It can come and go, it can never be seen again after this, and it doesn't necessarily cause problems for all CFers in terms of chronic coughs ect.
Hang in there...
Warmly,
Jody mom of Julia 6 no cf, Ben 22 months w/cf