In this clinical trial we will test a new approach for decolonization of S. aureus.

As innovative product HY-133 a recombinant chimeric bacteriophage endolysin will be sprayed in both nostrils of healthy subjects once or five times in one day. To avoid possible bias the subjects will be randomized 3:2 verum vs placebo, moreover the subject as well as the investigator will be blinded to the group assigned.

Inclusion Criteria

• Must be ≥ 18 years at the time of signing the informedconsent.
• Understand and voluntarily sign an informed consent document prior to any study related
• assessments/procedures.
• Nasal colonization with methicillin-susceptible S. aureus (MSSA)
• Female Subject of childbearing potential1 and male subjects with female partner of childbearing potential1 is willing to use highly effective contraceptive methods during treatment until end of study at D15

Exclusion Criteria

• Nasal colonization with methicillin-resistant S. aureus (MRSA)
• Nasal traumata including nose penetrating foreign bodies (e.g. piercings)
• Presence of any significant morbidity, e.g. Diabetes, cardiovascular disease
• Acute or known chronic diseases of the nose or the paranasal sinuses
• Acute or known chronic diseases of other parts of the respiratory tract
• Running nose due to other reasons (e.g. allergic diseases)7. Positive serological HIV, hepatitis A, B or C test. In case of positive HBsAg, volunteer must provide prove of hepatitis B vaccination, otherwise volunteer must be excluded.
• Women during pregnancy and lactation.
• History of hypersensitivity to the investigational medicinal product or to any drug with similar chemical structure or to any excipient present in the pharmaceutical form of the investigational medicinal product.
• Participation in other clinical trials or observation period of competing trials, in the 12 weeks prior to screening.
• Acute or chronic, clinically significant psychiatric, hematologic, pulmonary, cardiovascular, or hepatic or renal functional abnormality as determined by the Investigator based on medical history, physical exam, and/or laboratory screening test
• Systemic antibiotic treatment in the 12 weeks prior to screening.
• Intranasal eradication therapy in the 12 weeks prior to screening.