552. Real-Time Polymerase Chain Reaction Detection of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Colonization at Admission during Universal Screening Predicts Subsequent Infection at a Military Hospital
Session: Poster Abstract Session: MRSA Surveillance and Infection Prevention
Friday, October 21, 2011
Room: Poster Hall B1
  • IDSA2011POSTER552.pdf (133.7 kB)
  • Background: The risk of subsequent methicillin-resistant Staphylococcus aureus (MRSA) infection following a positive nasal polymerase chain reaction (PCR) assay on hospital admission remains unclear.  Our institution implemented universal MRSA surveillance by XpertTM MRSA assay (Cepheid) at admission starting in January 2009.    The purpose of this study was to determine the risk of MRSA infection among PCR surveillance positive patients over a six month period in the setting of universal screening.

    Methods: This was a retrospective study of all hospitalized patients who underwent admission nasal MRSA PCR testing from January 1, 2009 to August 31, 2010.  MRSA colonized patients were defined as those with a positive admission surveillance nasal PCR.  They were placed on contact isolation but no routine decolonization was performed.   MRSA infections were defined by a positive MRSA culture in association with a clinical decision to treat.  Only MRSA infections with a concurrent or preceding surveillance PCR result were included.   Patient characteristics such as age, ward, antibiotic use, surgeries, diabetes, or war trauma were collected via chart review.   The odds ratio was determined by the Mantel-Haenszel test. 

    Results: The nasal MRSA colonization rate among all admitted patients during the study period was 6.31% (6849 screened, 432 positives).  Of the 432 MRSA PCR positive patients, 47 developed subsequent MRSA infection (10.88%).  Of the 6417 negatives, 43 developed MRSA infection (0.67%).  This resulted in an odds ratio of 18.096 (95% CI: 11.816-27.713, P< 0.05).  Among the 90 patients with MRSA infection who qualified for the study, there were 67 men and 23 women, and the median age was 59 years.  The average time between screening PCR result and MRSA infection was 30.8 days (range 0-174).   Wound infections were the most common diagnosis, followed by bacteremia.       

    Conclusion: In this study, a positive nasal MRSA PCR on admission strongly predicted the development of MRSA infection among adult patients within a 6 month period.  These results are similar to reports using nasal culture, and support the supposition that MRSA colonization is a risk factor for subsequent invasive infection. 

    Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

    Leyi Lin, MD1, Susan Fraser, MD2 and Glenn Wortmann, MD2, (1)Infectious Diseases, Walter Reed Army Medical Center, Washington, DC, (2)Walter Reed Army Medical Center, Washington , DC


    L. Lin, None

    S. Fraser, None

    G. Wortmann, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.