567. Risk of Methicillin-Resistant Staphylococcus aureus (MRSA) Surgical Site Infection (SSI) in Patients with Nasal MRSA Colonization
Session: Poster Abstract Session: MRSA Surveillance and Infection Prevention
Friday, October 21, 2011
Room: Poster Hall B1
  • IDSA_Final.pdf (394.0 kB)
  • Background: Methicillin-resistant Staphylococcus aureus (MRSA) surgical site infections (SSI) lead to substantial morbidity, mortality and economic burden. MRSA-colonized patients are at higher risk for invasive infection as compared with non-colonized patients. Nasal colonization of MRSA is common among inpatient populations, but the extent to which nasal carriers are at increased risk of MRSA SSI is unclear.

    Methods:We conducted a retrospective cohort study to assess occurrence of MRSA SSI among inpatients who underwent MRSA PCR testing of the anterior nares and surgical procedure(s) at our 500-bed tertiary care center between April 2008-July 2010. Only principal procedures under surveillance by National Health Safety Network (NHSN) criteria were included. Patients were classified into two groups based on the following definitions, MRSA PCR screen-positive patients: Patients with a positive MRSA PCR who underwent a surgery on the same day as the positive PCR or within the subsequent 30 days.  MRSA PCR screen-negative patients: Patients with a negative MRSA PCR who underwent a surgery on the same day as the negative PCR or within the subsequent 30 days. Outcome: The primary outcome assessed was MRSA SSI as defined by NHSN surveillance criteria. The follow-up period was April 2008 - December 2010.

    Results:31,269 patients underwent MRSA PCR screening; 2196 (7%) had at least one positive test. Of inpatients with a positive MRSA PCR, 401 underwent surgery within the next 30 days and 8 (2.00%) subsequently developed MRSA SSI. Of 8,487 patients who had only negative MRSA PCR(s) in the 30 days prior to surgery, 19 (0.22%) developed MRSA SSI (RR=8.91, 95%CI=3.92, 20.2, p value<0.0001). Vancomycin was used on day of surgery in 19.5% of the MRSA screen-positive patients, and in 10.2% of MRSA screen-negative patients.

    Conclusion:Patients with a positive nasal MRSA PCR result were at 9 times greater risk of subsequent development of MRSA SSI compared to patients with a negative nasal MRSA PCR result. However, since the absolute risk of MRSA SSI in screen-positive patients appears to be low (1.8%), identifying subsets of these patients at highest risk of SSI may help to target decolonization and other interventions. 

    Subject Category: C. Clinical studies of bacterial infections and antibacterials including sexually transmitted diseases and mycobacterial infections (surveys, epidemiology, and clinical trials)

    Lalit Kalra, MD1, Cynthia Whitener, MD1, Margaret Miller, MT(ASCP)M2, Ping Du, MD, PhD3, Marissa Grifasi, PharmD4, Crystal Zalonis, DO1 and Kathleen G. Julian, MD5, (1)Internal Medicine/Infectious Diseases, Penn State Milton S. Hershey Medical Center, Hershey, PA, (2)Infection Control, Penn State Milton S. Hershey Medical Center, Hershey, PA, (3)Medicine/Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA, (4)Pharmacy, Penn State Milton S. Hershey Medical Center, Hershey, PA, (5)Medicine/Infectious Diseases, Penn State Hershey Medical Center, Hershey, PA


    L. Kalra, None

    C. Whitener, None

    M. Miller, None

    P. Du, None

    M. Grifasi, None

    C. Zalonis, None

    K. G. Julian, 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.