Clinical Characteristics and Outcomes of Carbapenem-Resistant Gram-Negative Bacteria Pneumonia in Immunocompromised ICU Patients: A Retrospective Study

Background: Immunocompromised patients are increasingly admitted to intensive care units (ICUs), where carbapenem‑resistant Gram‑negative bacteria (CRGNB) pneumonia poses a growing threat due to limited treatment options and high mortality. This study aimed to compare the characteristics and outcomes of immunocompromised and immunocompetent ICU patients with CRGNB pneumonia and identify risk factors for ICU mortality. Methods: We retrospectively analyzed the clinical characteristics, laboratory findings, and outcomes of patients with laboratory‑confirmed CRGNB pneumonia admitted to Third Affiliated Hospital of Sun Yat‑sen University from January 2021 to April 2025. Results: Among 185 patients, 83 (44.9%) were immunocompromised, most often due to corticosteroid use (33.7%) or cancer chemotherapy (27.7%). Compared with immunocompetent patients, immunocompromised patients had higher rates of viral co-infection (36.1% vs 20.6%, p = 0.029), bacteremia (39.8% vs 15.7%, p < 0.001), and ICU mortality (65.1% vs 26.5%, p < 0.001). Escalation therapy was observed more commonly in immunocompromised patients (79.5% vs 61.8%, p = 0.014). In multivariate analysis, ICU mortality among immunocompromised patients was independently associated with vasopressor therapy (OR = 4.53, 95% CI: 1.35– 16.85, p = 0.01), the ratio of invasive mechanical ventilation time to ICU length of stay (IMV time/ICU LOS) (OR = 1.18, 95% CI: 1.01– 1.40, p = 0.04), age > 65 years (OR = 3.59, 95% CI: 1.20– 12.14, p = 0.02), and platelet count < 100 × 10 9 /L (OR = 3.26, 95% CI: 1.02– 12.12, p = 0.04). Among immunocompetent patients, vasopressor therapy (OR = 37.76, p < 0.001), CRRT (OR = 16.60, p = 0.001), pre-existing heart failure (OR = 3.26, p = 0.049), and IMV time/ICU LOS (OR = 1.48, p < 0.001) were independent mortality predictors, while tracheostomy was protective (OR = 0.13, p = 0.016). Conclusion: Immunocompromised ICU patients with CRGNB pneumonia have distinct clinical characteristics, higher mortality, and risk factors that should be incorporated into prognostic evaluation and management. Keywords: intensive care unit, immunocompromised, carbapenem-resistant gram-negative bacteria, pneumonia, retrospective study