Hi Debbie...
I'm not sure I know what you mean? Are you talking like how do you know when you colonize pseudo, etc.? I thought it was just done with a sputum test being sent to the lab and seeing what is growing. For example, when they do sensitivity testing when you're sick with an exacerbation, they take your sample and send it in and see what is growing, how much, and what medication it would respond to. I know when I was younger and couldn't always cough up a sample, they either didn't know what I was growing and just tried meds to see if they'd work (or a couple of times they tried to suction to get a sample, which was extremely traumatizing to me).
I'm not sure this is what you're asking, but I hope it helps! <img src="i/expressions/face-icon-small-smile.gif" border="0">