Differences in Pre- and Post-dischcarge Methicillin-resistant Staphylococcus aureus (MRSA) infection rates by colonization status in US Department of Veterans Affairs (VA) hospitals

BACKGROUND: Little is known about how MRSA infection rates differ between patients who are colonized on admission compared with those who acquire colonization during an inpatient stay. In addition, most studies focus on MRSA infections that are diagnosed prior to discharge while ignoring those that are identified post-discharge. The VA implemented an active surveillance program for MRSA in 2007 in which all inpatients are tested for MRSA on admission. This surveillance data along with the ability to follow patients longitudinally allowed us to estimate the difference in infection rates for those who import vs. those who acquire MRSA colonization during their stay and to characterize post-discharge MRSA infections. METHODS: We constructed a dataset of 3,659,911 acute care inpatient admissions to 125 VA hospitals nationwide between January 1, 2008 and December 31/2015 who had surveillance tests performed for MRSA carriage. Admissions were restricted to individuals with at least 365 days of VA activity prior to admission. We categorized these admissions into 3 groups: no colonization, importation, and acquisition based on MRSA test results throughout the admission. We then captured MRSA infections in these individuals prior to discharge and at 30 and 90 days post-discharge. Infections were defined as positive MRSA cultures taken from sterile sites (including blood, catheter site, or bone). RESULTS: During the 8-year period, we identified 4,037 total pre-discharge MRSA infections, 2,793 MRSA infections at 30 days post-discharge, and 7,018 infections at 90 days post-discharge. During the pre-discharge time period, patients who acquired MRSA carriage were more likely to progress to an infection prior to discharge than those who imported the pathogen (RR = 2.6, P < 0.001). For patients who acquired MRSA carriage, the percentage who progressed to infection prior to discharge decreased from 2.0% in 2010 to 1.4% in 2015. The results from our analyses can be found in Figures 1–3. CONCLUSION: We found that roughly half of post-discharge infections were in patients who acquired the organism pre-discharge. These may be preventable with optimal infection control. In addition, there were nearly twice as many post-discharge MRSA infections at 90 days than during the pre-discharge period. DISCLOSURES: All authors: No reported disclosures.