Impact of Pseudomonas aeruginosa carriage on ICU-acquired pneumonia: a European multicentre prospective cohort study.

Objectives: Pseudomonas aeruginosa (PA) is a common causative pathogen of pneumonia acquired in the ICU. The aim of this study was to determine the incidence of PA ICU pneumonia (PAIP) and to quantify its independent association with PA colonisation at different body sites.

Methods: Adult patients on mechanical ventilation at ICU admission were prospectively enrolled across 30 European ICUs. PA colonisation in the perianal area and in the lower respiratory tract were assessed within 72 hours after ICU admission and twice weekly until ICU discharge. PAIP development was evaluated daily. Competing risk models with colonisation as a time-varying exposure and ICU death and discharge as competing events were fitted and adjusted for confounders to investigate the association between PA carriage and PAIP.

Results: 1971 subjects were enrolled. The colonisation prevalence with P. aeruginosa in the first 72 hours of ICU admission was 10.4% (179 perianal, 51 respiratory), while the acquisition incidence during the ICU stay was 7.0% (158 perianal, 47 respiratory). Of the 43 (1.8%) patients who developed PAIP, 11 (25.6%) were PA colonised on admission and 9 (20.9%) acquired colonisation prior to PAIP onset. Both perianal (adjusted sub distribution hazard ratio [aSHR] 4.4, 95%CI 1.7-11.6) and respiratory colonisation (aSHR 4.6, 95%CI 1.9-11.1) were independently associated with PAIP development.

Conclusions: PAIP incidence was higher in PA colonised vs non-colonised patients. Both colonisation of the rectum and of the respiratory tract were associated with development of PAIP. The increased risk of P. aeruginosa colonisation for subsequent infection provides an opportunity for targeted preventive interventions.