Pathogen characteristics and pre-index clinical factors associated with multidrug-resistant organism infections in intensive care unit patients

Multidrug-resistant organism (MDRO) infections remain a major cause of healthcare-associated morbidity in intensive care units (ICUs). Local characterization of pathogen profiles and clinical factors associated with MDRO infection is needed to inform infection prevention and antimicrobial stewardship strategies.

This single-center retrospective observational study included consecutive adult ICU admissions from January to December 2025 with an ICU length of stay ≥48 h and available microbiological cultures. MDRO infection was defined according to clinical infection criteria and phenotypic non-susceptibility to at least one agent in ≥3 antimicrobial categories. A 1:2 propensity score matching approach was used to reduce baseline imbalance. Univariable and multivariable logistic regression analyses were performed to identify pre-index clinical factors associated with MDRO infection, and model discrimination was assessed using receiver operating characteristic (ROC) analysis.

Among 986 eligible patients, 103 developed MDRO infection, yielding an incidence of 10.4%, with a median onset of 6 days after ICU admission. MDRO infections were mainly ventilator-associated/hospital-acquired pneumonia and bloodstream infection. Carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Enterobacterales, and carbapenem-resistant Pseudomonas aeruginosa were the predominant phenotypes. In the matched cohort (n = 309), pre-index clinical factors independently associated with MDRO infection included Acute Physiology and Chronic Health Evaluation II score (adjusted odds ratio [aOR] 1.04), pre-ICU antibiotic exposure (aOR 1.58), pre-index ICU carbapenem exposure (aOR 1.92), total pre-index systemic antibiotic duration in ICU (aOR 1.11 per day), pre-index mechanical ventilation (aOR 2.06), pre-index continuous renal replacement therapy (aOR 1.69), procalcitonin (aOR 1.39), and albumin (aOR 0.93). The model showed good discrimination, with an area under the ROC curve of 0.836 and a bootstrap-corrected value of 0.821.

MDRO infections occurred in approximately one-tenth of ICU admissions and were primarily Gram-negative respiratory and bloodstream infections. Illness severity, pre-index antimicrobial exposure intensity and duration, pre-index organ support, and early inflammatory or nutritional biomarkers were independently associated with MDRO infection. These findings may support preliminary ICU risk stratification, but prospective validation and formal time-dependent exposure assessment are warranted.