Multi-centre study of the in vitro activity of ceftolozane/tazobactam and other commonly used antibiotics against Pseudomonas aeruginosa isolates from patients in the United Kingdom (INVICTUS)

Study type

• Study type:
  Not applicable
• Scope of the study:
  Effectiveness study (incl. comparative)
• If ‘Not applicable’, further details on the study type:
  In vitro susceptibility testing

Population studied

• Age groups:
  Adults (18 to < 46 years)

  Adults (46 to < 65 years)

  Adults (65 to < 75 years)

  Adults (75 to < 85 years)

  Adults (85 years and over)
• Estimated number of subjects:
  1400

Study design details

• Main study objective:
  To evaluate the in vitro activity of ceftolozane/tazobactam and other commonly used antipseudomonal antibiotics against geographically spread P. aeruginosa bacterial isolates in the UK.
• Data analysis plan:
  This is a descriptive in vitro analysisMethods to Minimize Bias: Consecutive isolates from individual centres will reduce the likelihood of centres picking specific patient or sample types. Sub-group analysis will also help analyse the characteristics of specific isolates based on antibiogram and sample type. Limitations: The study is a mostly retrospective analysis of unselected stored bacterial isolates from multiple laboratories with heterogeneous patient populations and differing criteria for storing isolates. It is therefore inherently susceptible to selection bias as above. However, it will provide a real-world analysis of clinically significant isolates and allows for sub-group analysis. Inter-laboratory variability in susceptibility testing performance is well established when performing phenotypic analysis of bacterial isolates, results for cystic fibrosis isolates are especially prone to this issue. External quality control will assess any significant variation.