Program Schedule

Risk of Methicillin-Resistant Staphylococcus aureus Infection in Patients with Intermittent versus Persistent Nares Colonization

Session: Poster Abstract Session: MRSA and VRE
Thursday, October 9, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
Background: Prevention of methicillin resistant Staphylococcus aureus (MRSA) infection is of concern in healthcare settings.  More information is needed about the relationship between MRSA colonization and infection, in order to inform prevention efforts.  Among patients followed longitudinally, risk of methicillin sensitive S. aureus (MSSA) infection is similar among non-colonized (NC) and intermittently colonized (IC) patients, and higher among persistently colonized (PC) patients. Previous studies of S. aureus infection in NC persons versus those with an IC or PC phenotype have not included patients with MRSA colonization, and have been limited to patients on peritoneal dialysis. We compared the incidence of MRSA infection in patients who were screened longitudinally over 41 months, and classified as PC, IC or NC.

Methods: Observational study of 3,873 patients who had > or = 5 MRSA nasal colonization screening tests collected longitudinally from 2/20/2010 through 7/26/2013.  Invasive infections were identified using the CDC National Healthcare Safety Network definitions. PC patients had > or = 80% of screening tests positive, NC patients had all negative screening tests. IC patients had > 0 and < 80% of screening tests positive. Kaplan-Meier time-to-event analysis was used to determine the relative risks of infection in PC, IC, and NC patients.

Results: 103 patients developed invasive MRSA infections, 16.3% of PC, 11.3% of IC, and 0.5% of NC patients. PC patients were at higher risk of invasive infection than NC patients, for any given period of time-at-risk (HR 39.2, 95%CI 19.6-78.4, p<0.001).  IC patients were at higher risk than NC patients (HR 23.8, CI 13.8-40.9, p<0.001).  The difference in risk between PC and IC patients was not statistically significant (HR 1.65, CI 0.96-2.84, p=0.071).

Conclusion: Among the general patient population of this tertiary care medical center, invasive MRSA infection occurred frequently in both persistently and intermittently colonized patients.  There was a higher rate of infection in those who were PC when compared with IC individuals, but the difference was not statistically significant.  These results suggest that the risk of MRSA infection is similar among persistently colonized and intermittently colonized patients.

Daniel I. Vigil, MD, Department of Preventive Medicine, University of Colorado-Denver, Aurora, CO, Wesley D. Harden, MD, Preventive Medicine, University of Colorado-Denver, Aurora, CO, Anne E. Hines, PhD, Research, DVAMC-Denver, Denver, CO and Mary T. Bessesen, MD, VA Eastern Colorado Health Care System and University of Colorado School of Medicine, Denver, CO


D. I. Vigil, None

W. D. Harden, None

A. E. Hines, None

M. T. Bessesen, None

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