Seventeen Years of an Antibiotic Stewardship Programme: Trends in Antibiotic Prescribing and Gram-Negative Bacilli Susceptibility at a Quaternary Healthcare Institution

<b>Background/objectives:</b> Studies evaluating the longitudinal impact (beyond a decade) of antibiotic stewardship programs (ASPs) on the volume/quality of antibiotic prescriptions, as well as the impact on antibiotic resistance, are lacking. Since 2008, the ASP at Singapore General Hospital has implemented various strategies in the following phases: (1) initiation, (2) expansion, (3) optimisation, and (4) innovation. In this study, we aim to evaluate the volume/quality of antibiotic prescribing and susceptibility trends of clinically significant Gram-negative bacilli (GNBs), along with the evolution of ASP strategies over time. <b>Methods:</b> We conducted a single-centre, retrospective observational study from 2011 to 2024. Antibiotic consumption, appropriateness, and susceptibility trends of six GNBs to seven commonly used antibiotics were analysed using the <i>Kendall tau</i> test to identify potential monotonic trends based on aggregated rather than patient-level data. <b>Results:</b> We demonstrated sustained improvement in appropriateness of seven broad-spectrum IV antibiotics, accompanied by significant reductions in IV ciprofloxacin, cefepime, and ertapenem use (<i>p</i> < 0.05). Hospital-wide susceptibility of six GNBs to all evaluated antibiotics improved significantly (<i>p</i> < 0.05), except for <i>E. coli</i>'s susceptibility to ertapenem and <i>Enterobacterales</i>'s susceptibility to ciprofloxacin. <b>Conclusions:</b> With an evolving, multi-pronged stewardship approach, antibiotic prescribing and GNB susceptibility to most antibiotics have improved. In a rapidly evolving healthcare landscape, ASPs must remain agile, continually refining priorities and employing innovative strategies.