Management of infections caused by Gram-negative bacteria in severely immunocompromised hosts employing Outpatient Parenteral Antimicrobial Therapy (OPAT): Preliminary evidence from a real-world observational study

Introduction Infections caused by Gram-negative bacteria pose a significant challenge in immunocompromised patients. Outpatient Parenteral Antimicrobial Therapy (OPAT) has emerged as a promising alternative to inpatient care, allowing patients to receive intravenous antimicrobial therapy at home while potentially improving their quality of life. However, data on the efficacy and safety of OPAT in immunocompromised patients remain limited. This study aims to evaluate the effectiveness, safety, and clinical outcomes of OPAT in this vulnerable population. Methods We conducted a retrospective observational cohort study at a teaching hospital in Rome from 2020 to 2024. We included immunocompromised adult patients (≥18 years) with Gram-negative bacterial infections treated with OPAT. The primary effectiveness endpoint was treatment response. Safety endpoints included adverse events and complications. Results A total of 149 immunocompromised patients were included, with a median age of 64 years. The most common infections were urinary tract infections (51.7%) and bloodstream infections (16.8%). The most frequently isolated pathogens were Escherichia coli (41.9%), Klebsiella spp. (22.8%), and Pseudomonas aeruginosa (19.1%). The overall clinical cure rate was 88.6% (132/149), while 4.0% (6/149) experienced treatment failure and 3.4% (5/149) had infection recurrence within 60 days. Nearly all patients (91.9%) completed their OPAT treatment course without interruptions. Hospital readmission occurred in 7.4% (11/149) of cases. Complications were rare (5/149, 3.4%). Conclusion OPAT proved to be an effective and safe strategy for managing Gram-negative infections in immunocompromised patients. Close clinical and laboratory monitoring contributed to favorable outcomes. Further studies are needed to optimize OPAT protocols in this population.