Changes in Antimicrobial Resistance in Bloodstream Infections During the COVID-19 Pandemic—A Retrospective Study from a Tertiary Care Hospital

The COVID-19 pandemic led to major repurposing of healthcare settings, especially Infectious Diseases hospitals, by redirecting care towards SARS-CoV-2-infected patients. However, frequent bacterial infections overlapping the viral background led to changes in antimicrobial resistance profiling among patients. This study aims to assess isolates from invasive infections and their antimicrobial susceptibility patterns in pre-pandemic and pandemic periods. Positive blood cultures from patients hospitalized in our Institute between January 2019 and September 2022 were assessed in terms of antimicrobial susceptibility, following sample processing as per laboratory protocol, with the use of the automated Bactalert®3D system, MALDI-TOF® MS and microscopy for bacterial identification. Antimicrobial susceptibility testing was performed using the Vitek2Compact® and Micronaut-S® systems. Phenotypic enzyme production testing was assessed using the Resist-5 OKNVI kits. All data were subsequently digitalized, and statistical analysis was performed. A total of 932 non-duplicated bacterial and fungal strains were analyzed, with the most commonly isolated organisms being Staphylococcus aureus (n = 173), followed by Escherichia coli(n = 156), Acinetobacter baumannii (n = 95), and Klebsiella pneumoniae (n = 89). Resistance rates to multiple antimicrobials increased substantially amongst Klebsiella pneumoniae and Acinetobacter baumannii. Methicillin-resistant Staphylococcus aureus isolates followed a national decrease trend during the pandemic period; however, an increasingly resistant profile to macrolides may be attributable to the excessive and often unjustified use of Azithromycin during the pandemic period. The COVID-19 pandemic was accompanied by a shift in bacterial profile of invasive infections amongst our cohort, illustrating the dynamic nature of antimicrobial resistance in an Infectious Diseases hospital during those times, underscoring the complex interplay between the COVID-19 pandemic and antibiotic resistance patterns, and highlighting the need for ongoing surveillance and tailored antimicrobial stewardship efforts in clinical practice.