1. Cystic Fibrosis DepartmentInstitute of Mother and Child Warsaw Poland
2. Cystic Fibrosis CenterChildren's Hospital in Dziekanów Leśny Warsaw Poland
3. Department of Bacteriology and Biocontamination ControlNational Institute of Public Health—National Institute of Hygiene Warsaw Poland
4. Department of Epidemiology and BiostatisticsInstitute of Mother and Child Warsaw Poland
5. Independent Laboratory of Microbiology, Central Laboratory, Institute of Mother and Child Warsaw Poland