Divergent Organism-Specific Trajectories of Multidrug Resistance Across the COVID-19 Pandemic: An Interrupted Time-Series Study in a Mexican Tertiary Hospital, 2017-Early 2026

Background/Objectives: Whether the COVID-19 pandemic uniformly increased antimicrobial resistance (AMR) is contested, and aggregate analyses may mask organism-specific patterns. The objective of the study was to characterize changes in the level and slope of monthly multidrug-resistant (MDR), possible extensively drug-resistant (pXDR), possible pandrug-resistant (pPDR), vancomycin-resistant enterococci (VRE), and methicillin-resistant Staphylococcus aureus (MRSA) positivity at a Mexican tertiary-care hospital, and to assess heterogeneity by organism, antimicrobial class, specimen type, and hospital service.

Methods

Retrospective interrupted time-series of deduplicated bacterial isolates (October 2017 to January 2026), analyzed by segmented regression across pre-pandemic, pandemic, and post-peak phases.