Harvey,
When Sean was first diagnosed at 12 weeks old, we were told he cultured PA. I couldn't find any info on it and everytime I asked the Dr. I got the run around. I finally got a resident to tell me something about it but what he told me totally freaked me out.
So, here's what I know now...
Basically CFers cutlure (in their sputum) all kinds of bugs. The more "mild" bugs are the viral type followed by staph followed by PA (non-mucoid then mucoid) then, if you're really lucky, you can culture Cepacia. There is also MRSA and I think that falls into the category of "Superbug" just like Cepacia. There are all types of Cepacia and new info is being discovered everyday. This is still a "relatively" new discovery in the CF world. It used to be considered a death sentence but isn't anymore.
Cepacia was once thougth to be from the PA family but that has been disproven.
Once PA becomes mucoid (i.e. colonized), it starts to cause some serious damage and is resistant to meds. The idea is to prevent it from colonizing, hence the introduction of inhaled Tobi.
Most Dr.'s subscribe to the theory that once you culture PA you always have PA even if it doesn't show up on your culture.
As far as preventing it, good luck. PA lives everywhere, especially kitchens and bathrooms. It loves to grow in water/moist/damp areas. It's also very prevalent in hospitals as are most bugs.
I know there are plenty of folks on here that know more than I so hopefully, they'll chime in.