Unfortunately cystics are always fighting one form of infection or another. It is common for cystics to colonize bacteria as well, such as
pseudomonas aeruginosa, staph aureus and others because the lungs are a perfect breeding ground for bacteria due to the sticky mucous. I personally grow out B. cepacia (not a very nice bug), staph, steno. maltophillia (sp?) and pseudomonas about every time they culture me. When I get sick, the colonies are usually much higher and I have to get IV antibiotics.