Four-year antibiogram analysis of priority pathogens: guiding empirical therapy and monitoring resistance trends

ABSTRACT Antibiograms are essential surveillance tools for monitoring institutional antimicrobial resistance (AMR) patterns and supporting antimicrobial stewardship programs (AMS). This study analyzed 4 years (2020–2023) of cumulative and subtraction antibiograms to describe local susceptibility trends among priority bacterial pathogens in a tertiary-care teaching hospital in western India. A retrospective observational study was conducted using the first-isolate-per-patient-per-year methodology in accordance with Clinical and Laboratory Standards Institute (CLSI) M39 guidelines. Antimicrobial susceptibility testing was performed using disk diffusion and automated minimum inhibitory concentration (MIC)-based systems, with colistin tested exclusively by broth microdilution. Cumulative and subtraction antibiograms were generated for Escherichia coli , Klebsiella pneumoniae , Pseudomonas aeruginosa , Acinetobacter baumannii , Staphylococcus aureus , and Enterococcus species. Data were analyzed descriptively. A total of 5,530 priority pathogen isolates were included. Gram-negative organisms demonstrated high resistance to fluoroquinolones, third-generation cephalosporins, and carbapenems, particularly K. pneumoniae , consistent with a substantial carbapenem-resistant Enterobacterales burden. Non-fermenters showed persistently low β-lactam susceptibility. Glycopeptides and linezolid retained high in vitro activity against gram-positive organisms. Colistin and tigecycline demonstrated high in vitro susceptibility across several multidrug-resistant organisms; however, year-to-year variability and fluctuating isolate numbers limit interpretation of temporal changes. This study highlights a sustained burden of AMR and underscores the importance of continuous, standardized antibiogram surveillance. Antibiogram data should inform stewardship strategies and institutional policy but must be interpreted alongside the clinical context and infection-control measures rather than used in isolation to determine empirical therapy. IMPORTANCE Antimicrobial resistance (AMR) is a growing global health threat that makes common infections harder to treat and increases the risk of severe illness and death. Hospitals must continuously monitor local resistance patterns to ensure antibiotics remain effective. This study analyzes 4 years of hospital laboratory data to track how bacteria responded to commonly used antibiotics over time. The findings reveal a sustained burden of resistance, particularly among gram-negative organisms, highlighting the need for ongoing surveillance and responsible antibiotic use. By systematically evaluating cumulative and subtraction antibiograms, this work demonstrates how routine laboratory data can support antimicrobial stewardship programs (AMS) and guide institutional policy. Importantly, the study emphasizes that antibiograms should inform stewardship strategies rather than dictate treatment decisions in isolation. Continuous monitoring and careful interpretation of resistance trends are essential to preserving the effectiveness of existing antibiotics and strengthening infection-control efforts.