The most likely source of the problem was that she inhaled an old mixture. Premixed Colistin MUST be used within 7 days. That's why I prefer to mix my own--I know exactly when I mixed it, and what concentration I used.
Like Amy, I'm skeptical of the info. It looks like this was an isolated incident. Especially considering that I have no found any of the information about this anywhere other than here. There's nothing on SourceCF's site, nothing on Medwatch, or CFF or FDA. I also couldn't find any information about the doctors whose names appear in that email some of you received.
Again, this appears to be an isolated incident. Certainly it's a serious one, which is why it's purportedly being investigated. I'll make my final conclusions when I see some proof-positive documentation.