Pseudomonas aeruginosa in Patients With Nosocomial Respiratory Infections: A Secondary Analysis of the European Network for ICU-Related Respiratory Infections

Abstract

Background: Nosocomial respiratory infections (NRIs) are the most common complication among patients in the ICU, with Pseudomonas aeruginosa frequently identified. However, the global prevalence of P aeruginosa and associated risk factors remain unclear.

Research question: Among patients in the ICU with NRI, what is the international prevalence of P aeruginosa, and which clinical factors are associated with an increased risk?

Study design and methods: This secondary analysis used data from the European Network for ICU-Related Respiratory Infections, a prospective cohort study conducted across 12 countries from May 2016 through August 2019. Data from 1,059 patients with NRI who underwent microbiological testing were analyzed. Descriptive statistics, imputation of missing data, least absolute shrinkage and selection operator regression, elastic net, random forest, and multivariable logistic regression were applied. Model performance was assessed using McFadden's R² and the Hosmer-Lemeshow test.

Results: The median patient age was 64 years (interquartile range, 49-73 years), and 72% were male. Pathogens were identified in 67% of patients (710 of 1,059), primarily using blood culture samples (78%). P aeruginosa was detected in 14.5% of samples (n = 153), with antimicrobial resistance mechanisms in 5.1% of samples (n = 55). Among these, 19.6% of samples were multidrug resistant and 11.1% of samples produced carbapenemase. The highest prevalence was observed in Germany, Argentina, and France. Ventilator-associated pneumonia was the predominant diagnosis, accounting for 66% of P aeruginosa cases. Septic shock and acute kidney injury (AKI) were the most frequent complications. No significant mortality differences were found between patients with and without P aeruginosa infection. Key risk factors included COPD Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage D, autoimmune disease, chronic kidney disease (CKD), and AKI on day 1.

Interpretation: P aeruginosa is a leading NRI pathogen, with prevalence varying across countries. A high proportion of patients receive empirical anti-Pseudomonas treatment without confirmed infection by P aeruginosa. Key risk factors identified for Pseudomonas NRI were COPD GOLD stage D, autoimmune disease, CKD, and AKI. These findings support the need for more personalized, evidence-based empirical therapy.

Clinical trial registration: ClinicalTrials.gov; No.: NCT03183921; URL: www.

Clinicaltrials: gov.

Keywords: LASSO regression; Pseudomonas aeruginosa; elastic net regression; nosocomial respiratory infections; random forest; risk factors.