Risk of MRSA Infection in Patients with Intermittent versus Persistent MRSA Nares Colonization.
OBJECTIVE
To determine the relative risk of invasive methicillin-resistant Staphylococcus aureus (MRSA) infection among non-colonized (NC) patients, intermittently colonized (IC) patients, and persistently colonized (PC) patients.


METHODS
Observational cohort study of patient data collected longitudinally over a 41-month period.


METHODS
Department of Veterans Affairs Eastern Colorado Healthcare System, a tertiary care medical center.


METHODS
Any patient who received ≥5 MRSA nasal swab tests between February 20, 2010, and July 26, 2013. In total, 3,872 patients met these criteria, 0 were excluded, 95% were male, 71% were white, and the mean age was 62.9 years on the date of study entry.


METHODS
Patients were divided into cohorts based on MRSA colonization status. Physicians reviewed medical records to identify invasive infection and were blinded to colonization status. Cox and Kaplan-Meier analyses were used to assess the relationship between colonization status and invasive infection.


RESULTS
In total, 102 patients developed invasive MRSA infections, 16.3% of these were PC patients, 11.2% of these were IC patients, and 0.5% of these were NC patients. PC patients were at higher risk of invasive infection than NC patients (hazard ratio [HR] 36.8; 95% CI, 18.4-73.6; P<.001). IC patients were also at higher risk than NC patients (HR, 22.8; 95% CI, 13.3-39.3; P<.001). The difference in risk between PC and IC patients was not statistically significant (HR, 1.61; 95% CI, 0.94-2.78, P=.084). Alternate analysis methods confirmed these results.


CONCLUSIONS
The risk of invasive MRSA infection is much higher among PC and IC patients, supporting routine clinical testing for colonization. However, this risk is similar among PC and IC patients, suggesting that distinguishing between the 2 colonization states may not be clinically important.
1University of Colorado,Preventive Medicine Residency,Aurora,Colorado.
Daniel I
DI
Vigil
1University of Colorado,Preventive Medicine Residency,Aurora,Colorado.
Wesley D
WD
Harden
2Veterans Health Administration Eastern Colorado Healthcare System,Infectious Disease,Denver,Colorado.
Anne E
AE
Hines
3University of Colorado,Adult and Child Center for Outcomes Research and Delivery Science,Aurora,Colorado.
Patrick W
PW
Hosokawa
3University of Colorado,Adult and Child Center for Outcomes Research and Delivery Science,Aurora,Colorado.
William G
WG
Henderson
2Veterans Health Administration Eastern Colorado Healthcare System,Infectious Disease,Denver,Colorado.
Mary T
MT
Bessesen
D000368:Aged; D002353:Carrier State / Q000382:microbiology*; D003120:Colorado; D003428:Cross Infection / Q000453:epidemiology*; D005260:Female; D006787:Hospitals, Veterans / Q000706:statistics & numerical data; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data; D053208:Kaplan-Meier Estimate; D008137:Longitudinal Studies; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008875:Middle Aged; D009296:Nasal Cavity / Q000382:microbiology*; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000453:epidemiology*