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A mathematical model quantifying the impact of antibiotic exposure and other interventions on the endemic prevalence of vancomycin-resistant enterococci.

D'Agata EM, Webb G, Horn M

Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA. edagata@bidmc.harvard.edu

BACKGROUND: Mathematical modeling can be used to describe the interdependent and dynamic interactions that contribute to the transmission dynamics of vancomycin-resistant enterococci (VRE). A model was developed to quantify the contribution of antibiotic exposure and of other modifiable factors to the dissemination of VRE in the hospital setting. METHODS: The model consists of 4 compartments: patients colonized with VRE receiving and not receiving antibiotics and uncolonized patients receiving and not receiving antibiotics. A series of differential equations describe the movement between these compartments. Baseline parameter estimates were obtained from pharmacy, infection-control, and clinical databases. RESULTS: The main predictions of this model are that (1) preventing the initiation or enhancing the discontinuation of unnecessary antimicrobial therapy will have a greater impact if it is targeted to patients who are not colonized with VRE; (2) increasing the number of patients harboring VRE at the time of hospital admission substantially increases the endemic prevalence of VRE; and (3) eliminating the influx of VRE results in the eradication of this pathogen from the hospital. A decrease in the endemic prevalence of VRE also occurs with a decrease in the length of hospital stay of colonized patients, increased hand hygiene compliance, and a lower ratio of health-care workers : patients. CONCLUSION: This mathematical model provides a framework to assist in targeting necessary interventions aimed at limiting the spread of VRE.

Published 3 November 2005 in J Infect Dis, 192(11): 2004-11.
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