Patient Factors Associated With Antimicrobial Utilization in the Solid Organ Transplant Population.

Background: The U.S. Centers for Disease Control and Prevention, through the National Healthcare Safety Network (NHSN), developed antimicrobial utilization (AU) metrics for hospital reporting and benchmarking. We applied this framework, using a modified NHSN definition of inpatient AU, to identify factors associated with antimicrobial use among solid organ transplant (SOT) recipients. Methods: We conducted a retrospective single-center cohort study of first adult SOT recipients from 2010 to 2019. Inpatient AU during the first 6 months post-transplant was calculated as facility-wide days of therapy (DOT) per 1000 patient-days using a modified NHSN definition. Organ-specific multiple linear regression identified baseline characteristics associated with AU. Results: Among 1845 recipients (293 heart, 531 kidney, 426 liver, and 595 lung), AU varied by organ: heart 560, kidney 285, liver 622, and lung 1111 DOT/1000 patient-days. In heart recipients, pretransplant infection requiring intravenous antibiotics and longer ischemic time were associated with higher AU, while transplant year, A-blood group, and medical condition at transplant predicted lower AU. In lung recipients, ischemic time increased AU, whereas age and lung allocation score decreased AU. In liver recipients, only the transplant year was associated with lower AU. In kidney recipients, ischemic time was associated with increased AU, while transplant year, functional status, and insurance type were associated with lower AU. Conclusions: AU in the first 6 months post-SOT was substantial and varied by organ type, with specific baseline characteristics influencing its use. Applying AU metrics to SOT populations can inform targeted antimicrobial stewardship interventions.