Risk Factors for Extended-Spectrum β-lactamase, Carbapenem, and Colistin Resistance Among Enterobacterales Bloodstream Infections in Intensive Care Units

bloodstream infections (E-BSIs) in intensive care units (ICUs) are increasingly complicated by antimicrobial resistance. This retrospective study evaluated resistance patterns and phenotype-specific risk factors for extended-spectrum β-lactamase (ESBL) production and carbapenem and colistin resistance in 314 adult ICU patients with monomicrobial E-BSI admitted to a tertiary care hospital in Türkiye between September 2019 and 2022. Resistance rates were calculated using evaluable isolates, and independent risk factors were identified by multivariable logistic regression. ESBL positivity was detected in 179 of 312 isolates (57.4%), phenotypic carbapenem resistance in 84 of 311 (27.0%), and colistin resistance in 100 of 272 isolates (36.7%). Compared with antibiotic-susceptible patients, those with at least one resistance phenotype had a longer admission-to-blood-culture interval and more frequent prior antibiotic exposure. Admission-to-blood-culture interval, malignancy, and purulent endotracheal secretions were independently associated with ESBL positivity; respiratory failure and tigecycline use within the previous 3 months were independently associated with colistin resistance; and central nervous system disease and hemodialysis were independently associated with carbapenem resistance. ICU-associated E-BSI exhibited substantial antimicrobial resistance, with distinct phenotype-specific risk profiles supporting early risk stratification and targeted antimicrobial stewardship interventions.