Impact of Pharmacist-Involved Antimicrobial Stewardship Interventions on Clinical and Process Outcomes in Multidrug-Resistant Organism Infections: A Systematic Review and Meta-Analysis

Background/Objectives: Antimicrobial resistance (AMR) is a major global health threat, and multidrug-resistant organisms (MDROs) are associated with worse outcomes than susceptible infections. Pharmacists are central to antimicrobial stewardship (AMS), yet their impact in confirmed MDRO infections is unclear. We evaluated pharmacist-involved AMS on clinical and process outcomes in MDRO infections and quantified pooled effects on clinical outcomes. Methods: Following PRISMA 2020, seven databases were searched (inception–December 2025) for pharmacist-involved AMS studies in patients with confirmed MDRO infections (Tier A) or in mixed populations from which MDRO-specific outcomes were extractable (Tier B), classified into Tier A, B, or C by outcome extractability. Random-effects meta-analyses were performed a priori for outcomes with ≥2 studies, with fixed-effect sensitivity and GRADE ratings. Results: Forty-nine studies were included (7 Tier A, 6 Tier B, 36 Tier C); quantitative synthesis was restricted to the 13 Tier A/B studies with MDRO-specific outcome data, and certainty of evidence was very low for all five pooled outcomes. Pharmacist involvement consistently improved process outcomes (time to therapy, de-escalation, antimicrobial consumption) and reduced mortality and readmissions in several subgroups. Pooled random effects RRs (95% CI) were: 30-day mortality, 0.64 (0.41–1.00; I2 = 28%, non-significant); in-hospital mortality, 0.72 (0.57–0.92; I2 = 6%, significant); 30-day readmission, 0.50 (0.31–0.79; I2 = 0%, significant); recurrent infection, 0.51 (0.25–1.04); and acute kidney injury, 1.01 (0.54–1.87; both non-significant, I2 = 0%). Conclusions: Multicomponent AMS interventions involving pharmacists were consistently associated with improved stewardship processes and significant reductions in in-hospital mortality and 30-day readmission, though evidence certainty remained very low. Larger, prospective studies with harmonized outcome definitions are needed to confirm the clinical benefit’s magnitude.