Hi! Piper cultured pseudo until she was about 3 yrs old, and has cultured MRSA since she was 6. She stayed on the TOBI for 4 yrs after she stopped culturing pseudo, we took her off it for maybe 6 months, and re-started it because we could see a difference in the number of exacerbations she was having increasing. There is some thought that pseudo can be masked by MRSA. There's also the school of thought that just because something isn't showing on a culture, doesn't mean that it isn't there. Particularly with "cough" cultures, there's no way of knowing what part of the lungs the mucus is coming from, and what may be growing in a different place. I look at it as a better safe than sorry thing, particularly when we saw her health slide down when we stopped the TOBI. Maybe if you really want her off it, you can talk to the Drs about doing a trial run off it to see what happens. Hope this helps...