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MRSA colonization significantly increases risk for subsequent infection

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August 15, 2018

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Richard E. Nelson

MRSA colonization significantly increases the risk for subsequent MRSA infection during and after hospitalization, researchers reported in study findings published in Clinical Infectious Diseases.

“Using data from hospitalized patients in the Department of Veterans Affairs (VA) health care system, we estimated the relationship between MRSA colonization and pre- and post-discharge MRSA infections,” Richard E. Nelson, PhD, research health scientist in the IDEAS Center at the George E. Wahlen Department of Veterans Affairs Medical Center in Salt Lake City and research associate professor in epidemiology at the University of Utah School of Medicine, told Infectious Disease News. “We found that MRSA colonization significantly increases the risk of MRSA infection and that a substantial proportion of MRSA infections occur after discharge.”

According to Nelson and colleagues, since 2007, patients admitted, transferred between units or discharged from VA hospitals have been tested for MRSA carriage, providing information on MRSA acquisition during hospitalization.

For their study, they used the VA data to estimate the difference in infection rates for patients who were not colonized with MRSA; those who were colonized on admission, identified as importers; and those who acquired MRSA during their hospital stay. Patients were examined for MRSA infection before discharge and at 30, 90, 180 and 365 days after discharge.

They studied 985,626 first admissions to VA acute care hospitals between 2008 and 2015 who were tested for MRSA carriage, including 82,278 with direct ICU admission. There were 983,816 patients who did not have MRSA during hospitalization who were followed after discharge. These included 903,190 (91.6%) patients determined not be colonized with MRSA during hospitalization, 72,388 (7.3%) importers and 10,048 (1%) who acquired MRSA during their hospital stay.

The MRSA infection rate measured across the predischarge and 180-day postdischarge period was higher for patients admitted directly to the ICU. The rate was 5.5% in importers and 7% in acquirers who were not directly admitted to the ICU compared with 11.4% in importers and 11.7% in acquirers admitted directly to the ICU.

Importers had a predischarge HR for MRSA infection of 29.6 (95% CI, 26.5-32.9), whereas acquirers had an HR of 28.8 (95% CI, 23.5-35.3) in comparison to patients who were not colonized.

MRSA pre- and postdischarge infection rates within 180 days after discharge were 63.9% for importers and 61.2% for acquirers.

“Hospitalized patients who are colonized with MRSA, regardless of whether they were colonized on admission or acquired it during their inpatient stay, are at high risk for MRSA infection,” Nelson said. “In addition, subsequent MRSA infections may not manifest until after discharge. These factors should be taken into account when optimizing infection control strategies.” – by Bruce Thiel

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Disclosure: The researchers report no relevant financial disclosures.

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