Predictors of intensive care unit admission in patients with Legionella pneumonia: role of the time to appropriate antibiotic therapy

Abstract Purpose Legionella spp. pneumonia (LP) is a cause of community-acquired pneumonia (CAP) that requires early intervention. The median mortality rate varies from 4 to 11%, but it is higher in patients admitted to intensive care unit (ICU). The objective of this study is to identify predictors of ICU admission in patients with LP. Methods A single-center, retrospective, observational study conducted in an academic tertiary-care hospital in Pisa, Italy. Adult patients with LP consecutively admitted to study center from October 2012 to October 2019. Results During the study period, 116 cases of LP were observed. The rate of ICU admission was 20.7% and the overall 30-day mortality rate was 12.1%. Mortality was 4.3% in patients hospitalized in medical wards versus 41.7% in patients transferred to ICU ( p < 0.001). The majority of patients (74.1%) received levofloxacin as definitive therapy, followed by macrolides (16.4%), and combination of levofloxacin plus a macrolide (9.5%). In the multivariate analysis, diabetes (OR 8.28, CI 95% 2.11–35.52, p = 0.002), bilateral pneumonia (OR 10.1, CI 95% 2.74–37.27, p = 0.001), and cardiovascular events (OR 10.91, CI 95% 2.83–42.01, p = 0.001), were independently associated with ICU admission, while the receipt of macrolides/levofloxacin therapy within 24 h from admission was protective (OR 0.20, CI 95% 0.05–0.73, p = 0.01). Patients who received a late anti- Legionella antibiotic (> 24 h from admission) underwent urinary antigen test later compared to those who received early active antibiotic therapy (2 [2–4] vs. 1 [1–2] days, p < 0.001). Conclusions Admission to ICU carries significantly increased mortality in patients with diagnosis of LP. Initial therapy with an antibiotic active against Legionella (levofloxacin or macrolides) reduces the probability to be transferred to ICU and should be provided in all cases until Legionella etiology is excluded.