P. aeruginosa colonization at ICU admission as a risk factor for developing P. aeruginosa ICU pneumonia

OBJECTIVE: To determine the incidence of P. aeruginosa (PA) ICU pneumonia and its independent association with PA colonization at ICU admission. METHODS: This was a post-hoc analysis of a prospectively collected cohort study. Adult ICU patients with a length of stay of ≥48 h were included and assessed for microbiologically confirmed PA ICU pneumonia. Multivariate survival analysis was performed, including the covariates age, gender, PA colonization at ICU admission, ICU admission specialty and mechanical ventilation at ICU admission, while taking into account the effect of competing risks. RESULTS: We included 5093 patients, 2447 (48%) were tested for colonization; of those 226 (9.2%) were PA colonized at ICU admission. The incidence of PA ICU pneumonia was 1.34% (n = 68). PA colonization was an independent risk factor (subdistribution hazard ratio [SHR] 8.8; 95% confidence interval [CI] 4.9–15.7), as was mechanical ventilation (SHR 5.3, 95% CI 2.7–10.6). CONCLUSION: In this study the incidence of P. aeruginosa ICU pneumonia was 1.34%. Hazard ratios for PA colonized patients compared to non-colonized to develop PA ICU pneumonia were 8.8. The high risk associated with P. aeruginosa colonization for subsequent infection may offer a target for future interventions.