347. The methicillin-resistant Staphylococcus aureus (MRSA) nasal real-time PCR as a predictive tool for contamination of the hospital environment with MRSA
Session: Poster Abstract Session: MRSA, MSSA, Enterococci
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
  • IDSA_poster_MRSA_Livorsi.pdf (158.7 kB)
  • Background: We sought to determine whether the burden of MRSA in the nares, as determined by the cycle threshold (CT) value from real-time PCR, is predictive of extra-nasal colonization and environmental contamination with MRSA.

    Methods: Patients identified as MRSA nasal carriers at the time of either hospital admission or room transfer were enrolled within 72 hours.  Patients were excluded if 1) nasal mupirocin was used within the past month, 2) chlorhexidine body wash was used during the current hospital stay, or 3) an active MRSA infection was suspected at the time of enrollment.  Four environmental sites, 5 body sites and a wound (if present) were cultured with pre-moistened swabs in all patients.  All nasal swabs were submitted for both a quantitative culture and real-time PCR (Roche Lightcycler, Indianapolis, IN). 

    Results: 67 patients were enrolled between 7/1/2012 and 4/30/2013, of which 61 had MRSA-positive nasal swabs at the time of enrollment.  The median age was 64 years (IQR 59-74), and 60 (98%) were men. Forty-two (69%) patients had at least one extra-nasal body site colonized with MRSA, and 24 (39%) had at least one environmental site contaminated with MRSA.  In 9 cases tested, the nares and environmental isolate had an identical pattern on pulsed-field gel electrophoresis (PFGE).

    The median CT value was 29.9 (IQR 26.6-32.2).  There was a negative correlation between the CT value and the number of MRSA colonies in the nares (r2= −0.64, p<0.01).  Using a CT cut-off of 27, there was a significant difference between the number of environmental sites contaminated with MRSA (1.8 vs. 0.4, p<0.01) but not the number of body-sites colonized with MRSA (2.2 vs. 1.4, p=0.10).  The level of MRSA carriage varied by current use of antibacterial agents (no, CT 27.8 vs. yes, CT 30.0, p=0.02).  The Cvalue of researcher-collected nasal swabs was lower than that of hospital nurse-collected swabs (mean difference 2.0, p<0.01). 

    Conclusion: Patients with a higher burden of MRSA in their nares, as defined by a real-time PCR, are more likely to contaminate their hospital surroundings with MRSA.  The infection control implications of this finding warrant further study.

    Daniel Livorsi, MD1,2, Sana Arif, MD1, Patricia Garry2 and Sarah W. Satola, PhD3, (1)Medicine, Indiana University School of Medicine, Indianapolis, IN, (2)Richard Roudebush VA Medical Center, Indianapolis, IN, (3)Atlanta VAMC, Decatur, GA


    D. Livorsi, None

    S. Arif, None

    P. Garry, None

    S. W. Satola, None

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