561. Longitudinal Molecular Epidemiology of Methicillin-Resistant Staphylococcus aureus Isolates Colonizing and Infecting Marine Recruits
Session: Poster Abstract Session: MRSA Surveillance and Infection Prevention
Friday, October 21, 2011
Room: Poster Hall B1
  • 561_CareySchlett.pdf (977.1 kB)
  • Background: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) causes skin and soft tissue infections (SSTI) in military recruits.  Molecular methods such as pulsed-field gel electrophoresis (PFGE) characterize specific CA-MRSA types among isolates associated with invasive disease vs. colonization. As colonization can precede SSTI, insight into the longitudinal molecular epidemiology of colonization is important for disease prevention.

    Methods: A cluster-randomized, double-blind, controlled trial comparing the effectiveness of thrice-weekly chlorhexidine (CHG) cloths with control (Comfort Bath) in SSTI prevention was conducted in military recruits.  Baseline and serial nasal/axillary swabs assessed for CA-MRSA colonization.  Isolates were typed by PFGE.

    Results: Of the 1562 subjects enrolled, 32 (2.0%) were colonized with CA-MRSA at baseline, primarily with PFGE types USA800 (31%), USA100 (25%), USA1000 (16%), and USA300 (13%).  After 10 weeks, the CHG group had 68 follow-up CA-MRSA colonization episodes which included types USA800 (51.5%), USA100 (23.5%), USA300 (13.2%).  In contrast, the control group had 99 CA-MRSA colonization episodes which included types USA300 (40.4%), USA800 (38.4%), USA1000 (12.1%), and USA100 (6.1%). The mean cumulative incidence of USA300 colonization was lower in the CHG group than in the control group (0.9% vs. 3.6%, [P= 0.058]).

    Conclusion: Use of CHG caused a trend towards decreased acquisition of CA-MRSA type USA300 in military recruits.  Furthermore, increased colonization with less virulent types, namely USA800, was observed over time. Future studies should evaluate why colonization dynamics, and the impact of CHG on molecular epidemiology, varies by CA-MRSA type.  

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

    Timothy Whitman, DO1, Carey Schlett, MPH2, Greg Grandits, MS3,4, Eugene Millar, PhD5, Katrin Mende, PhD2, Duane Hospenthal, MD, PhD6, Patrick Murray, PhD7 and David Tribble, MD, DrPH8, (1)Infectious Diseases, Walter Reed National Military Medical Center, Bethesda, MD, (2)Inf Dis Clin Res Prg, Uniform Serv Univ, Bethesda, MD, (3)Infectious Disease Clinical Research Program, Minneapolis, MN, (4)Univ Minn, Minneapolis, MN, (5)Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, (6)San Antonio Military Medical Center, MCHE MDI 7 East, TX, (7)National Institutes of Health, Bethesda, MD, (8)IDCRP/Uniformed Services Univ. of the Hlth. Sci., Bethesda, MD


    T. Whitman, None

    C. Schlett, None

    G. Grandits, None

    E. Millar, None

    K. Mende, None

    D. Hospenthal, None

    P. Murray, None

    D. Tribble, 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.