Sen, Ayan

Abstract Background Legionella pneumonia is an important cause of severe pneumonia, yet contemporary data describing its clinical phenotype, diagnostic patterns, and outcomes in the modern era are limited. Methods We conducted a retrospective multicenter cohort study of adults with laboratory-confirmed Legionella pneumonia across an integrated health system between January 2019 and September 2025. The primary outcome was 30-day mortality. Severe disease was defined as having a requirement for high-flow nasal cannula, noninvasive ventilation, mechanical ventilation, or extracorporeal membrane oxygenation (ECMO). Univariate and multivariable logistic regression were used to identify predictors of mortality and severe disease. Results There were 344 patients with laboratory-confirmed Legionella pneumonia during the study period. The median age was 66.6 years, and 45.1% were immunocompromised. Most patients required hospital admission (94.2%), with 36.1% admitted to the intensive care unit; 22.7% required mechanical ventilation and 1.5% ECMO. Thirty- and 90-day mortality were 11.9% and 16.6%, respectively. In multivariable analysis, cirrhosis (OR 10.2, 95% CI 2.15–48.3, P = .003), immunocompromised status (odds ratio [OR] 2.24, 95% CI 1.05–4.77, P = .036), age (OR 1.03, 95% CI 1.00–1.06, P = .031), and lymphopenia at presentation (OR 2.09, 95% CI 1.02–4.24, P = .043) were independently associated with increased 30-day mortality. Among patients who were polymerase chain reaction (PCR) or culture positive, urinary antigen testing was positive in only 25.6%. Conclusions Legionella pneumonia was associated with substantial short-term mortality. Cirrhosis, age, immunocompromised status, and lymphopenia at presentation emerged as independent predictors of 30-day mortality, underscoring the importance of host vulnerability in determining outcomes.

ABSTRACT Background Solid organ transplant (SOT) recipients are at risk for Pneumocystis jirovecii pneumonia (PCP), yet how their clinical phenotype and outcomes compare with other immunocompromised patients without HIV remains poorly defined. Methods We conducted a multicenter retrospective cohort study of adults with proven or probable PCP from 2017 to 2025, including 95 SOT recipients and 588 non‐SOT, non‐HIV immunocompromised patients. The primary outcome was 90‐day mortality, secondary outcomes included new renal failure requiring dialysis, and 30‐day mortality. Outcomes were analyzed using inverse probability weighting (IPW) with winsorization to adjust for baseline differences. Results In unadjusted analysis, SOT recipients had lower 90‐day mortality (hazard ratio [HR]: 0.62, 95% CI 0.39–0.97, p = 0.037). After IPW with winsorization of extreme weights, SOT status remained associated with lower 90‐day mortality (HR: 0.32, 95% CI 0.13–0.76, p = 0.009), and 30‐day mortality (HR: 0.35, 95% CI: 0.14–0.92, p = 0.034). SOT recipients had higher odds of renal failure requiring dialysis in unadjusted analysis (OR: 3.49, 95% CI 1.94–6.14, p < 0.001), which persisted after IPW adjustment (OR: 1.62, 95% CI: 1.04–2.51, p = 0.032). Conclusions Despite higher rates of renal failure requiring dialysis, SOT recipients with PCP experienced significantly improved short‐ and intermediate‐term survival compared with other non‐HIV immunocompromised patients, underscoring the need for further investigation into transplant‐associated contributors to PCP outcomes.