Demographics and outcome of Legionella pneumonia in the intensive care unit: a retrospective multicenter cohort study

Background: Legionella pneumonia (LP) is a major cause of severe community-acquired pneumonia (CAP) that can lead to acute respiratory distress syndrome (ARDS) with high morbidity and mortality. ARDS may necessitate extracorporeal membrane oxygenation (ECMO) support, and evidence is limited about benefits of ECMO in LP. Therefore, we sought to analyze the clinical course, outcomes and predictive factors of ECMO patients with ARDS due to LP compared to non ECMO patients. Methods: This retrospective, multicenter cohort study analyzed ICU patients with LP across three tertiary university hospitals (Zurich, Switzerland; Hannover & Bonn, Germany) from 2013 to 2023. We examined demographics, clinical characteristics, and outcomes, with a focus on ECMO utilization and its impact on mortality. Results: A total of 110 patients were included, with a median age of 60 years and 75% male. ECMO support was initiated in 40%. The overall 28-day mortality did not differ between groups, with 21% without ECMO vs. 25% with ECMO (OR 1.24 (0.49-3.05, p = 0.64), despite higher degree of organ failure in the ECMO group (SOFA score 24 h after ICU admission 9 vs. 12, p < 0.001). Only 57% of patients had adequate antibiotic LP coverage at ICU admission with no differences in outcome. Multivariable analysis found hospital acquired LP (OR 28.4 (3.44-614), p = 0.006) and lactate (OR 1.31 (1.05-1.75), p = 0.031) as independent risk factor for 28-day mortality. Conclusions: Patients suffering from LP requiring ECMO support had similar mortality rates compared to LP patients without ECMO support, despite higher SOFA scores. In addition, LP-induced respiratory failure requiring ECMO had a lower mortality rate compared to the published literature on the overall ARDS population. This indirect indication of a potential survival benefit may support bedside clinicians in their decision-making regarding ECMO initiation or withholding.