# Clinical Outcomes and Predictors of Mortality in Patients with Difficult-to-Treat Resistant Pseudomonas aeruginosa Infections: A Retrospective Cohort Study

## TL;DR

This study finds that septic shock and older age increase mortality in hard-to-treat Pseudomonas infections, while newer antibiotics may improve survival.

## Contribution

Identifies clinical predictors of mortality and response to therapy in DTR-PA infections using a real-world cohort.

## Key findings

- Thirty-day all-cause mortality was 49% in patients with DTR-PA infections.
- Septic shock was an independent predictor of mortality, while targeted therapy with β-lactam/β-lactamase inhibitors showed a protective trend.
- Clinical cure was negatively associated with device burden and bloodstream infection.

## Abstract

Background: Difficult-to-treat resistant Pseudomonas aeruginosa (DTR-PA) infections are associated with high morbidity and mortality, but data on prognostic factors remain limited. Given the limited real-world data on outcomes of DTR-PA infections, we aimed to identify clinical predictors of mortality and response to therapy in this setting. Methods: We conducted a single-center retrospective cohort study of 51 patients with DTR-PA infections. The primary endpoint was 30-day all-cause mortality; secondary endpoints were clinical and microbiological cure at end of therapy. An exploratory analysis evaluated 30-day infection-related mortality. Logistic regression models (univariable, multivariable and Firth bias-reduced) were used to identify independent predictors. Results: Median age was 64 years (IQR 22); 63% were male and 71% were in the ICU at infection onset. Sepsis occurred in 80% and septic shock in 45%. Thirty-day all-cause mortality was 49% (25/51). According to multivariable analysis, septic shock was an independent predictor of mortality (aOR 5.52, 95% CI 1.04–29.27; p = 0.045) as younger age (aOR 1.06, 95% CI 1.00–1.12; p = 0.052), whereas targeted therapy with ceftazidime/avibactam or ceftolozane/tazobactam is a protective factor (aOR 0.15, 95% CI 0.02–1.17; p = 0.070) did not reach significance in the final model. Clinical cure occurred in 33% (17/51) and was negatively associated with device burden and bloodstream infection, whereas microbiological cure (45%, 23/51) was more likely with targeted therapy and absence of sepsis. The exploratory analysis of infection-related mortality (35%) showed similar predictors. Conclusions: DTR-PA infections are associated with high mortality. Septic shock and older age predict death, while the use of novel β-lactam/β-lactamase inhibitors is associated with improved outcomes. Early recognition of severe illness and timely administration of active therapy may improve survival in these infections.