The primary objective of this trial is to assess the safety and tolerability of single and multiple ascending intravenously (IV) infused doses of CTX-187 when administered to healthy adult male and female participants and participants with a bacterial infection (bronchiectasis participants chronically infected with P. aeruginosa).

Inclusion Criteria

1. Parts A and B: Healthy adult males and/or females, 18 to 65 years of age.
2. Parts A and B: Body mass index (BMI): ≥18.0 and ≤32.0 kg/m^2 and weight >50 kg.
3. Parts A and B: Good physical and mental health without clinically significant abnormalities.
4. Part C: Adult males and/or females, 18 to 75 years of age.
5. Part C: Prior clinical and computerized tomography diagnosis of bronchiectasis.
6. Part C: P. aeruginosa in sputum, bronchoalveolar lavage or another airway sample at least once in the 12 months prior to screening and P. aeruginosa in sputum during screening, both of which should be at least 21 days apart.
7. Part C: Otherwise in good physical and mental health without clinically significant abnormalities.

Exclusion Criteria

1. Parts A and B: Previous participation in the current trial.
2. Parts A and B: History or presence of significant cardiovascular, pulmonary, hepatic, renal, haematological, gastrointestinal, endocrine, immunologic, dermatologic, or neurological disease, including any acute illness or surgery within the past 3 months determined by the Investigator to be clinically relevant.
3. Parts A and B: Participation in a drug trial within the previous 30 days before the first dose of trial drug or 5x elimination half-life, if known, whichever is longer.
4. Part C: Known hypersensitivity to any reagents contained in CTX-187 or documented hypersensitivity reaction or anaphylaxis to any medication.
5. Parts A, B and C: Known clinical diagnosis of cystic fibrosis, active allergic bronchopulmonary aspergillosis or active tuberculosis or nontuberculous mycobacterial infection; primary diagnosis of asthma or chronic obstructive pulmonary disease.
6. Part C: Treatment with long term inhaled, systemic or nebulized anti-pseudomonal antibiotics which are newly initiated within the previous 3 months prior to screening.
7. Part C: Receipt of anti-pseudomonal antibiotics for an exacerbation during the screening period.
8. Part C: History or presence of unstable co-morbidities: cardiovascular, pulmonary, hepatic, renal, haematological, gastrointestinal, endocrine, immunologic, dermatologic, or neurological disease, including any acute illness or surgery within the past 3 months determined by the Investigator to be clinically relevant. Participants on stable doses of anti-hypertensive medications or statins may be included following discussion between the Investigator and the medical monitor.
9. Part C: History of known or suspected Clostridioides difficile infection or diarrhoea within one week of recruitment, not resolved during the past 5 days.
10. Part C: Participants with an acute exacerbation of bronchiectasis.