3086 — The Effectiveness of De-Colonization Added To Active Surveillance for Methicillin-Resistant Staphylococcus Aureus (MRSA): A Simulation-Based Approach

Rubin MA (IDEAS Center, VA Salt Lake City Health Care System), Walker B (IDEAS Center, VA Salt Lake City Health Care System), Harbarth S (University of Geneva, Geneva, Switzerland), Samore MH (IDEAS Center, VA Salt Lake City Health Care System)

Objectives:
Incorporating topical de-colonization to an active surveillance program to improve MRSA control remains controversial. We created a computer simulation of nosocomial MRSA transmission to explore the effect of a de-colonization policy on MRSA transmission.

Methods:
An agent-based simulation of individual patients, nurses, physicians, and rooms was designed. Patients were admitted with a baseline prevalence of MRSA carriage. Transient health care worker (HCW) hand carriage occurred upon contact with colonized patients or with contaminated environmental surfaces. Non-colonized patients acquired MRSA via contact with HCW or the environment. Two hospitals were simulated, each containing ICU and non-ICU wards. In both hospitals, patients classified as high risk for MRSA carriage at the time of admission underwent rapid testing and were placed on contact precautions if positive. In one hospital, these patients also underwent de-colonization. The effect of de-colonization was measured by comparing the rate of MRSA transmission (colonization plus clinical infection) between hospitals for each run, and was tested against a range of values for the effectiveness of contact isolation in a sensitivity analysis. Assumptions in the base case included: admission MRSA prevalence of 5%; effectiveness of de-colonization of 60%; and a contact rate ratio of 0.25.

Results:
In the base case scenario, de-colonization reduced the rate of MRSA transmission from 1.01 to 0.77 events/1,000 bed-days (P < 0.001). There was a linear relationship between the effectiveness of contact isolation and the difference in MRSA transmission between hospitals; as the effectiveness of contact isolation worsened, the impact of de-colonization increased (beta-coefficient, 1.07). At a contact rate ratio of 0.50, de-colonization reduced the rate of MRSA transmission by 0.45 events/1,000 bed-days. Threshold behavior was not observed.

Implications:
Incorporating a policy of MRSA de-colonization to ongoing active surveillance is likely to improve MRSA control in hospitals, particularly when the effectiveness of contact isolation is suboptimal.

Impacts:
A policy of MRSA de-colonization, as an adjunct to the current policy of active surveillance may be a consideration throughout the VA Health Care System to support the National MRSA Prevention Initiative. This study supports the testing of this hypothesis with a large clinical trial.