An observational study in Pseudomonas Infections, Pseudomonas Aeruginosa and Prognosis, sponsored by Centre Hospitalier Régional d'Orléans. Recruiting at 48 sites in 2 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-04-30.
Sponsored by Centre Hospitalier Régional d'Orléans · Observational
The primary objective of the ADDICT study is to assess and compare the clinical efficacy of available options for antimicrobial therapy (new beta-lactam/beta-lactamase inhibitor combination, cefiderocol or older agents such as aminoglycosides and colistin) in unselected patients with infection due to difficult-to-treat P. aeruginosa.
Infections due to Pseudomonas aeruginosa isolates with acquired resistances to all first-line antipseudomonal beta-lactams and fluoroquinolones (difficult-to-treat isolates - DTR), pose serious therapeutical challenges, especially in critically ill and/or immunocompromised patients. Certain new beta-lactam/beta-lactamase inhibitor combinations (BL/BLI (beta lactamine/ beta lactamase inhibitor) - i.e., ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam, others) and cefiderocol have shown promising results for the treatment of infections due to DTR P. aeruginosa. However, multicenter data on their real-life utilization in this indication are still scarce.
The ADDICT study is a prospective, multicenter cohort study including unselected patients with DTR P. aeruginosa infection requiring definite intravenous antimicrobial therapy. The primary objective of the study is to investigate the clinical efficacy of available options (new BL/BLI, cefiderocol or older agents such as aminoglycosides and colistin) in this population. Secondary objectives are to compare the clinical and microbiological efficacy of available options in infections due to DTR P. aeruginosa with in vitro susceptibility to more than one last-resort drug, to compare the incidence of non-ecological adverse events observed with these drugs, to assess the incidence of resistance emergence under therapy and to elucidate the molecular mechanisms of resistance emergence, to assess the benefits and risks of combination therapy in this indication, to compare the acquisition rates of multidrug-resistant bacteria other than DTR P. aeruginosa, and Clostridioides difficile infection, to compare Day-28 and in-hospital all-cause mortality rates.
Patients will be recruited in 60 hospital centers contributing to four French networks of research in infectious diseases and critical care (CRICS-TRIGGERSEP, ReaRezo, OutcomeRéa, RENARCI - PROMISE metanetwork). Clinical variables will be collected through an electronic case-report form. DTR P. aeruginosa isolates will be sent to the National Reference Center of Antimicrobial Resistance in P. aeruginosa for centralized analyses (extended antimicrobial susceptibility testing, MLST, whole-genome sequencing of successive isolates if resistance emergence under therapy).
136 studies on the registry are indexed under Pseudomonas Infections; 27 are open to participants now.
This study's planned enrollment of 600 is above the median of 100 across 38 observational studies indexed under Pseudomonas Infections.
Browse Pseudomonas Infections studies →Centre Hospitalier Régional d'Orléans is the lead sponsor of 132 studies on the registry; 32 are open to participants now.
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Prospective multicenter cohort
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Exclusion Criteria:
patients with invasive P. aeruginosa DTR infection requiring definitive intravenous antibiotic therapy
Clinical cure rate
Clinical responses will be assessed by local investigators. Clinical cure will be defined as a composite endpoint of survival with no relapse occurring since the end of definite therapy and the complete resolution of all initial clinical signs of infection at the ToC visit (all-cause deaths at the ToC visit will be considered as clinical failures).
Time frame: Test of cure visit
Clinical cure
Clinical responses will be assessed by local investigators. Clinical cure will be defined as a composite endpoint of survival with no relapse occurring since the end of definite therapy and the complete resolution of all initial clinical signs of infection at the ToC visit (all-cause deaths at the ToC visit will be considered as clinical failures).
Time frame: Day 7±2 after the completion of definite therapy
Microbiological eradication
Negativation of cultures for DTR P. aeruginosa in participants with at least one collected follow-up bacteriological sample (when clinically indicated) before the ToC visit
Time frame: Day 7
Resistance emergence
Any culture growing a DTR P. aeruginosa isolate with resistance to at least one new antimicrobial agent (compared to the first isolate) between the second day of definite therapy and hospital discharge
Time frame: Up to hospital discharge, an average of 1 month
Non-ecological adverse events
Any toxicity or allergic reaction attributed to the antimicrobial agent by the local investigator
Time frame: At test-of-cure visit, 7±2 days after the completion of definite therapy
Non-ecological adverse events
Any toxicity or allergic reaction attributed to the antimicrobial agent by the local investigator
Time frame: From the first day of definite therapy to the ToC visit
Acquisition of multidrug-resistant bacteria other than DTR P. aeruginosa
Culture of any clinical or surveillance sample growing a multidrug-resistant bacteria other than P. aeruginosa
Time frame: Up to hospital discharge, an average of 1 month
Clostridioides difficile infection
Documented C. difficile infection
Time frame: Up to hospital discharge, an average of 1 month
In-hospital death
All-cause death
Time frame: Up to hospital discharge, an average of 1 month
Death at Day 28
All-cause death
Time frame: Day 28
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