The purpose of this study is to prolong the time to reinfection with Pseudomonas aeruginosa after successfully treated acute or intermittent infection.

This is a double -blind, placebo controlled study in which the investigational drug and the reference placebo group are gargled and swallowed. 70 ml IgY/ placebo solution is gargled every night for two minutes (for maximal 24 months) The design will include the recruitment of 144 patients randomized in two groups (72 per treatment group) In order to compensate for dropouts (i.e. patients dropping out prior to 24 months without having an event) the total sample size was planned to be approximately 180 (i.e. ~20 % dropout rate). After the actual drop-out rate has been low throughout the study, only 144 plus approx. 10% potential drop-outs were included into the study.

During the two years of treatment, subjects will be examined at the clinic every 3 months regarding safety and efficacy of the medication.

For more information please see www.impactt.eu The IMPACTT Project is funded by EU within the Framework 7 Program. PsAer-IgY Studies is part of IMPACTT Project (Workpackage 2).

Inclusion Criteria:

• CF patients diagnosed according to specific clinical features and either a positive sweat chloride in double proofs or presence of disease-associated CFTR mutations in both alleles
• Males and females 5 years of age and above (being able to gargle)
• CF patients having a FEV1 value between 50% and 130% of predicted value (according to Knudson formula)
• CF patients who have had one to several sputum or throat cough swabs or endolaryngeal suction cultures positive for PA within the last three years and for whom PA has been successfully eradicated.
• Sputum / throat cough swab/ endolaryngeal suction culture negative for PA and other gram-negative bacteria on study entry.
• Patients and/ or their legal representative who are willing and able to give informed consent/ assent to participate in the study after thorough information
• Subjects of child bearing potential and who are sexually active must meet the contraception requirements (i.e. oral or injectable contraceptives, intrauterine devices, double-barrier method, contraceptive patch, male partner sterilization or condoms).

Exclusion Criteria:

• Microbiologic or serologic evidence of chronic infection with PA. Definition of chronic PA infection: Three cultures (sputum or throat cough swabs or endolaryngeal suction) have been positive for PA for 6 consecutive months (at least 3 cultures have to be taken) or more, .
• Patients, who have positive sputum culture or throat cough swab or endolaryngeal suction culture for gram-negative bacteria, such as PA, S. maltophilia, B. cepacia, A. xylosoxidans (eradication before entry in study is possible), Patients, who have positive sputum culture or throat cough swab or endolaryngeal suction culture for atypical Mycobacteria and / or Aspergillus fumigates, associated with clinical symptoms that may necessitate specific treatment.
• History of allergy/hypersensitivity to hens' egg proteins (including medication allergy) that is deemed relevant to the trial by the investigator. "Relevance" in this context refers to any increased risk of hypersensitivity reaction to trial medication.
• Patient with a known relevant substance abuse, including alcohol or drug abuse.
• Start of a new concomitant or chronic medication for CF within 4 weeks before inclusion.
• Clinically relevant diseases or medical conditions other than CF or CF-related conditions that, in the opinion of the investigator, would compromise the safety of the patient or the quality of the data. This includes, but is not limited to, significant hematological, hepatic, renal, cardiovascular, and neurological diseases (diabetic patients may participate if their disease is under good control prior to inclusion).
• Participation in another study with an investigational drug within one month or 6 half-lives (whichever is greater) preceding the inclusion.
• The patient is an employee of the investigator or the institution with direct involvement in the trial or other trials under the direction of the investigator or their members.
• Patients who are pregnant cannot be included into the study. This will be tested at inclusion visit with a urine pregnancy test (in female patients older than 10 years with secondary sexual characteristics)