A targeted stewardship intervention improves the adequacy of antipseudomonal therapy after implementation of the...

To evaluate the adequacy of antipseudomonal therapy in hospitalised patients following implementation of the 2019 EUCAST clinical category redefinitions through a multidisciplinary strategy.

A mixed-design study was conducted in a university hospital. Adult inpatients with documented Pseudomonas aeruginosa infection and available antimicrobial susceptibility and treatment data were included. Two study periods were defined: a pre-intervention retrospective/training period and a post-intervention period. Primary outcome was adequacy of antimicrobial therapy. Secondary outcomes included clinical and microbiological variables.

A total of 169 patients were included (78 pre-intervention and 91 post-intervention). Median age was 69 years (IQR 60-79), Charlson comorbidity index 5 (IQR 3-7) and SOFA score 3 (IQR 2-5). Analyses were adjusted for baseline differences between groups. Adequacy of antipseudomonal therapy increased significantly after the intervention (25/78 vs 79/91, p < 0.001). Interrupted time analysis (ITS) showed the intervention was associated with a marked and statistically significant immediate increase in the adequacy of antipseudomonal therapy (OR, 13.13; 95% CI, 1.73-113.25; p=0.015) after adjustment for time, SOFA score and infection type; without increased meropenem use. No significant differences were observed in mortality, readmissions or survival. Despite higher baseline severity in the post-intervention group, length of hospital stay was significantly shorter (OR = 0.98, p < 0.05). A non-significant trend toward fewer acquired resistance mutations was observed, consistent with improved local antipseudomonal susceptibility.

Implementation of the 2019 EUCAST clinical category redefinitions, supported by coordinated interventions from Microbiology and Infectious Diseases specialists, was associated with a marked improvement in adequate antipseudomonal therapy without increased meropenem use or adverse clinical outcomes. The trend toward reduced resistance emergence suggests this strategy is ecologically safe and sustainable.