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Epidemiology of resistant gram-negative bacteria in nursing homes

Published online by Cambridge University Press:  14 March 2023

John P. Mills*
Division of Infectious Diseases, Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey
Julia Mantey
Division of Geriatric and Palliative Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
Marco Cassone
Division of Geriatric and Palliative Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan
Keith S. Kaye
Division of Infectious Diseases, Department of Medicine, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey
Lona Mody
Division of Geriatric and Palliative Medicine, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan Veterans’ Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan
Author for correspondence: John P. Mills, MD, Division of Allergy, Immunology, & Infectious Diseases, Rutgers Robert Wood Johnson Medical School, One Robert Wood Johnson Place, Medical Education Building, Room 364, New Brunswick, NJ 08901. E-mail:



Resistant gram-negative bacteria (R-GNB) colonization in nursing home patients can cause clinical infection and intrafacility transmission. Limited data exist on the roles of age and function on R-GNB colonization.


A secondary data analysis was performed from a cohort study of 896 patients admitted to 6 Michigan nursing homes between November 2013 and May 2018. Swabs obtained upon enrollment, weekly for 1 month, then monthly until nursing home discharge from 5 anatomical sites were cultured for GNB. R-GNB were defined as resistant to ciprofloxacin, ceftazidime, or imipenem. Patients with growth of the same R-GNB as the initial positive visit, from any anatomical site at any subsequent visit, were considered persistently colonized. Demographic data, antibiotic use, device use, and physical self-maintenance scales (PSMSs) were obtained upon enrollment. Characteristics were compared between patients with R-GNB colonization versus those without, and those with persistent R-GNB colonization versus those with spontaneous decolonization.


Of 169 patients with a positive R-GNB culture and ≥2 subsequent study visits, 89 (53%) were transiently colonized and 80 (47%) were persistently colonized. Compared to uncolonized patients, persistent and transient R-GNB colonization were associated with higher PSMS score: 1.14 (95% confidence interval or CI, 1.05–1.23; P = .002) and 1.10 (95% CI, 1.01–1.19; P = .023), respectively. Persistent colonization was independently associated with longer duration of nursing home stay (1.02; 95% CI, 1.01–1.02; P < .001). Higher readmission rate among persistently colonized patients was observed on unadjusted analysis.


Persistent R-GNB colonization is associated with younger age, functional disability, and prolonged length of nursing home stay. In-depth longitudinal studies to understand new acquisition and transmission dynamics of R-GNB in nursing homes are needed.

Original Article
© The Author(s), 2023. Published by Cambridge University Press on behalf of The Society for Healthcare Epidemiology of America

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