Your son sounds a lot like me. I've cultured PA a couple times and have always managed to knock it out with tobi and a course of cipro (knock on wood). I take tobi every other month because, when I was 8ish, I took it to get rid of PA and whenever they tried to take me off for more than a month I would get sick even though I didn't grow PA again. Same kind of thing now-I'll get sick, they'll start me on IVs for both staph and pseudo, cancel the pseudo abx when I don't culture it, and I get sicker. The theory my docs have been using for years (justifying my staying on tobi) is that I grow so much staph/mrsa that it covers up either PA or some other gram-negative bacteria, but that the mystery bacteria makes me sick despite its small numbers. I know it sounds crazy that whatever I'm growing would stay hidden for so long, but I've had three docs at three centers come up with the same theory. It just isn't worth the drop in lung function to stop taking tobi and twiddle my thumbs getting sicker until I grow something new. I hope you get your son's problems figured out so he can start feeling better!
