764: Resistance Trends Before and After Covid-19: A Comparative Antibiogram Study From 2016-2023

Introduction: The COVID-19 pandemic disrupted infection control, antimicrobial prescribing, and lab workflows. While early reports suggested increased resistance due to broader empiric therapy and prolonged hospitalizations, real-world longitudinal antibiogram data remain limited. We analyzed local susceptibility trends before and after COVID-19 using recalculated, clinically representative metrics to assess true shifts in resistance. Methods: Antibiotic susceptibility data were extracted from institutional antibiograms (2018–2023). Pre-COVID data were defined as 2018–2019; post-COVID as 2021–2023. The year 2020 was excluded to avoid transitional confounding. ESBL and non-ESBL isolates for E. coli and Klebsiella pneumoniae were combined to reflect clinical decision-making and avoid overestimating resistance. Staphylococcus aureus resistance was tracked via oxacillin susceptibility as a proxy for MRSA prevalence. For Pseudomonas aeruginosa, tobramycin replaced amikacin per the 2024 CLSI guidance. Susceptibility percentages were compared using chi-square testing; trends were assessed with linear regression. Results: Among E. coli isolates (n≈3,200 pre; n≈2,900 post), cefepime susceptibility declined from 99% to 85% (p=0.04); levofloxacin declined from 80% to 76% (p=0.08). K. pneumoniae (n≈1,600 pre; n≈1,400 post) maintained high cefepime susceptibility (98% to 90%, p=0.06), and levofloxacin remained ≥94% post-COVID (p=0.15). For S. aureus (n≈1,200), oxacillin susceptibility remained stable at 98–99% (p=0.87), suggesting no significant change in MRSA prevalence. P. aeruginosa (n≈700) retained high tobramycin susceptibility (96–98%, p=0.53). Conclusions: Recalculated data showed a modest post-COVID decline in cefepime activity for E. coli, while K. pneumoniae, S. aureus, and P. aeruginosa remained broadly stable. Earlier antibiogram formats overstated resistance due to separate ESBL reporting. Findings suggest the pandemic’s impact on ICU resistance may be less than initially feared. Standardized reporting is essential to avoid unnecessary empiric changes and guide stewardship. This study is limited by its retrospective, single-center design and lack of patient-level data.