Investigation of antibiotic resistance against pathogens isolated from respiratory samples in intensive care units after SARS-CoV-2 pandemic.

backgroundThe COVID-19 pandemic has introduced major disruptions in clinical practices, including infection management strategies and antibiotic prescribing habits. This study aimed to investigate changes in the distribution of respiratory pathogens and their antimicrobial resistance (AMR) patterns in intensive care units (ICUs) before and after the onset of COVID-19 pandemic.

methodsIn this retrospective cross-sectional study, 1,662 respiratory tract samples (bronchoalveolar lavage, deep tracheal aspirate, and sputum) collected from ICU patients at a tertiary hospital in Turkey between January 1, 2016 and December 31, 2024 were analyzed. The study compared bacterial isolates and resistance profiles between the pre-pandemic (January 2016-Feb 2020) and post-pandemic (Mar 2020-December 2024) periods.

resultsAcinetobacter baumannii and Klebsiella pneumoniae remained the most frequently isolated pathogens throughout the study. Post-pandemic, resistance rates increased significantly for several antibiotics, particularly against Acinetobacter baumannii (gentamicin: 70.9% to 91.3%, p < 0.001; colistin: 3.2% to 12.3%, p < 0.001) and Klebsiella pneumoniae (carbapenems: p < 0.001; colistin: 23% to 62.7%, p < 0.001). For Pseudomonas aeruginosa, meropenem, piperacillin-tazobactam, and ceftazidime resistance rates increased significantly after the post-pandemic period (33.9% to 52.0%, p = 0.003; 50.4% to 65.1%, p = 0.011; 27.9% to 56.4%, p < 0.001, respectively). The changes in resistance rates of Escherichia coli were not statistically significant and also showed a reduced isolation rate post-pandemic (11.4% to 7.0%, p < 0.05). Among Gram-positive isolates, only Enterococcus faecium showed a significant increase in vancomycin resistance (50.0% vs. 0%, p = 0.046). In contrast, no significant findings were observed for methicillin resistance in Staphylococcus aureus (MRSA) and vancomycin resistance in Enterococcus faecalis (31.3% vs. 28.0%, p = 0.823; and 25% vs. 0%, p = 0.285, respectively). Mortality also increased significantly during the post-pandemic period (70.5% to 74.9%, p = 0.048), alongside a higher prevalence of comorbidities such as hypertension and coronary artery disease.

conclusionsThe findings highlight a marked escalation in AMR following the COVID-19 pandemic, likely driven by increased empirical antibiotic use, prolonged ICU stays, expanded use of invasive procedures, and broader steroid administration. This study underscores the deepening AMR crisis in ICUs and provides critical data from Turkey that may support global antimicrobial stewardship efforts.