Outpatient Parenteral Antimicrobial Therapy for Pseudomonas aeruginosa Infections: Effectiveness and Safety

Objective: Given the increasing use of outpatient parenteral antimicrobial therapy (OPAT) and the clinical challenges posed by Pseudomonas aeruginosa infections, this study aimed to evaluate the effectiveness and safety of OPAT for the treatment of P. aeruginosa infections in a real-world cohort. Methods: We conducted a prospective observational study with retrospective analysis including adult patients with P. aeruginosa infections treated within a multidisciplinary OPAT program shared by two tertiary hospitals between November 2012 and December 2024. Clinical characteristics, infection type, antimicrobial therapy, resistance patterns, source control, and clinical outcomes were recorded. Primary outcomes were treatment failure during OPAT and within 30 days after OPAT completion. Secondary outcomes included adverse events and vascular access complications. Bivariate and multivariable logistic regression analyses were performed to identify factors associated with treatment failure. Results: A total of 290 patients were included. The most frequent infections were bronchiectasis exacerbations (39.7%) and complicated urinary tract infections (15.2%). Most patients received monotherapy (72.8%), mainly ceftazidime, while 27.2% received combination therapy with a beta-lactam plus an aminoglycoside. Treatment failure occurred in 7.6% of patients during OPAT and in 15.5% within 30 days after OPAT completion, with an overall clinical success rate of 77%. Male sex and chronic obstructive pulmonary disease (COPD) were independently associated with failure during OPAT. At 30 days, higher Charlson comorbidity index, COPD exacerbation, and endovascular infection were associated with failure, whereas combination therapy was associated with a lower risk of failure. Antimicrobial-related adverse events were rare (3.2%). Conclusions: Our results support OPAT as an effective and safe strategy for managing P. aeruginosa infections in clinically stable patients. Patients with COPD, either as a comorbidity or during an exacerbation, and those with a higher Charlson score may require closer follow-up.