Epidemiological trends in bacterial resistance in diabetic foot infections across the COVID-19 timeline: a retrospective analysis

• Six-year analysis of AMR trends in diabetic foot infections • Decline in MRSA and CRPA across COVID-19 timeline • Emerging carbapenem resistance in Enterobacterales • Polymicrobial infections decreased post-pandemic • Long-term surveillance informs antimicrobial stewardship Diabetic foot infections (DFIs) are a major complication of diabetes mellitus and are frequently associated with multidrug-resistant (MDR) pathogens, contributing to increased morbidity and healthcare costs. Temporal variations in healthcare delivery and antibiotic use during recent years have raised concerns regarding potential changes in the epidemiology and antimicrobial resistance (AMR) profiles of DFIs. This retrospective epidemiological study analyzed 1,748 bacterial isolates recovered from patients with DFIs treated at IRCCS MultiMedica (Milan, Italy) across three distinct periods: pre-COVID (June 2018–December 2019), COVID (January 2020–July 2022), and post-COVID (August 2022–June 2024). Microbiological identification and susceptibility testing were performed according to AMCLI and EUCAST guidelines. Statistical analyses were conducted using MedCalc software. A progressive reduction in polymicrobial infections was observed, decreasing from 36.7% in the pre-COVID period to 29.1% in the post-COVID period. Methicillin-resistant Staphylococcus aureus (MRSA) declined from 67% to 48%, and carbapenem-resistant Pseudomonas aeruginosa (CRPA) decreased from 25% to 7%. In contrast, carbapenem-resistant Klebsiella pneumoniae (CRKP) increased from 45% to 67%, while carbapenem-resistant Escherichia coli (CREC) emerged in the post-COVID period (0% to 13%). Phenotypic resistance to third-generation cephalosporins (3GC-R) in K. pneumoniae showed a numerical decrease (70% to 42%), whereas E. coli resistant to third-generation cephalosporins increased (9% to 46%). Over a six-year observation period, this study documents significant temporal variations in pathogen distribution and AMR patterns among DFIs. While reductions in selected resistance phenotypes were observed, resistance among Enterobacterales displayed heterogeneous and concerning trends. These findings highlight the dynamic nature of AMR in DFIs and support the need for continuous, long-term epidemiological surveillance to inform local antimicrobial management strategies