I know this is an old thread but I found it while looking for an answer to almost the same question. My daughter cultured PA 6 months ago. The first round of TOBI killed it or whatever it does and she did not culture it again until last month. This time the TOBI did not get rid of it. What does it mean to use an IV for this? Is it days in the hospital or what am I looking at? Her Dr. wanted to talk to the other CF doctors about what course of action they would take and are getting back to me tomorrow. Her Dr. said she would usually recommend an extended oral (of which I am clueless) before an IV. Any information is helpful.