Impact of an antimicrobial stewardship program on antimicrobial resistance patterns, multiple antibiotic resistance indices, clinical outcomes, and cost savings: A pre-post interventional study in the intensive care unit of a tertiary-care hospital in India.

Antimicrobial resistance (AMR) poses a major challenge to patient outcomes, particularly in resource-constrained settings with widespread antimicrobial misuse. Structured antimicrobial stewardship programs (AMSPs) are essential to optimize antimicrobial use and reduce resistance. This pre-post interventional observational study evaluated the impact of AMSP implementation on antimicrobial susceptibility patterns, multiple antibiotic resistance (MAR) indices, stewardship performance indicators, clinical outcomes, and antimicrobial expenditure in the medical and surgical intensive care units of a tertiary-care teaching hospital in India over a 12-month period (pre-AMSP: October 2024-March 2025; post-AMSP: April-September 2025). Standard microbiological methods and Clinical and Laboratory Standards Institute (CLSI) M100 guidelines were used for organism identification and antimicrobial susceptibility testing. Following AMSP implementation, culture positivity decreased from 53.2% to 41.8%, while MAR indices declined by 12-24% across major pathogens. De-escalation rates increased from 49.8% to 77.6% ( P = 0.01), guideline adherence improved from 75.2% to 89.1% ( P < 0.001), culture turnaround time compliance increased from 68% to 89% ( P = 0.01), and days of therapy per 1000 patient-days decreased from 82 to 64 ( P < 0.001). Infection-related mortality declined from 5.4% to 3.8% (odds ratio = 0.53, P = 0.011), hospital-acquired infections decreased from 58.2% to 41.8% (relative risk = 0.72, P = 0.018), and antimicrobial expenditure was reduced by 46.4%, corresponding to a monthly saving of ₹9.96 lakh. Implementation of a multidisciplinary AMSP was associated with significant improvements in microbiological, stewardship, clinical, and economic outcomes, supporting the feasibility and effectiveness of structured antimicrobial stewardship programs in tertiary-care hospitals with a high burden of antimicrobial resistance.