Context-specific impact of antimicrobial stewardship on antibiotic use and antibiotic resistance in hospitals in a lower-middle-income country: results from an implementation study with a controlled interrupted time series design in Viet Nam

Objectives We aimed to determine the effects of a 12-month antimicrobial stewardship (AMS) programme in two provincial-level general hospitals in Viet Nam, a lower-middle-income country. Methods We performed controlled interrupted time-series analyses to evaluate the intervention effects on antibiotic use in days of therapy (DOT) per 1000 patient-days, antibiotic non-susceptibility percentage and patient outcomes. In each hospital, four wards received the intervention, and four wards acted as controls. Pre-intervention periods began in January 2019 and continued to May 2020 (Hospital 1) and July 2020 (Hospital 2). Results Regarding antibiotic use, the intervention was associated with an immediate absolute reduction of 95.9 DOT/1000 patient-days (95%CI 10.9–180.8) in Hospital 1, while Hospital 2 showed no overall change but declining slopes in selected antibiotics including aminoglycosides and penicillin/beta-lactamase inhibitors. Escherichia coli showed decreasing non-susceptibility to aminoglycosides and third-generation cephalosporins in both hospitals. Carbapenem non-susceptibility increased for both E. coli and Klebsiella spp. in Hospital 2 but decreased for Klebsiella spp. in Hospital 1. Non-susceptibility of P. aeruginosa increased to carbapenems (Hospital 1), aminoglycosides, ciprofloxacin and ceftazidime (Hospital 2). Acinetobacter spp. showed increased non-susceptibility to aminoglycosides and piperacillin–tazobactam in Hospital 1 but decreased to carbapenems, ciprofloxacin and piperacillin–tazobactam in Hospital 2. No evidence of changes in mortality or hospitalization costs were observed in both hospitals. Conclusions The impact of AMS varied between the two hospitals, highlighting the context-specific nature of implementation. Sustained monitoring of antibiotic use and resistance is needed to support locally tailored interventions that respond to evolving resistance epidemiology.