Impact of COVID Pandemic on Epidemiology of Antibiotic Resistance in an Intensive Care Unit (ICU): The Experience of a North-West Italy Center

SARS-CoV-2 pandemic caused an increase in Intensive Care Unit (ICU) hospitalizations with rise in morbidity and mortality; nevertheless, there is still little evidence of pandemic impact on antibiotic resistance in ICU. Retrospective monocentric epidemiological study. All microorganisms isolated from all patients admitted to E.O. Galliera ICU from January 2018 to December 2022 were included. Antibiotic resistance (AR) profiles were evaluated. Aim of the study was to describe and analyze the impact of SARS-CoV-2 pandemic on ICU microorganisms resistance patterns. 1,771 microorganisms identified, 221 (12.47%) had resistant pattern (Resistant Organisms; ROs) isolated from 1,679 patients during 12,030 hospitalization days. The majority of ROs were Gram-negative (79.66% 2018, 77.29% 2019, 61.83% 2020, 62.56% 2021, 60.75% 2022), but increase of Gram-positive microorganisms was observed (20.34% to 39.25% between 2018-2022). Prevalence of AR was: 19.44% 2018, 11.54% 2019, 38.04% 2020, 34.15% 2021, 39.29% 2022 for Gram-positives; 19.86%, 13.56%, 18.12%, 12.41%, 12.31% for Gram-negatives. Incidence of Ros showed COVID-related rise in 2020-2021, followed by a lowering trend since 2021, with new rise in 2022. Possible explanations are antibiotic overtreatment and drop of containing measures. Interesting finding is the cumulative lowering trend of carbapenem resistant K. pneumoniae and P. aeruginosa probably due to different patient features.