844. Prevalence of Staphylococcus aureus nasal colonization in military trainees with first-episode S. aureus skin infection
Session: Oral Abstract Session: MRSA - Epidemiological Trends
Saturday, October 22, 2011: 8:45 AM
Room: 157ABC
Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of skin and soft-tissue infection (SSTI) in military personnel.  Although antecedent nasal colonization with MRSA appears to be a risk factor for SSTI, simultaneous nasal colonization at the time of infection seems surprisingly uncommon. The contribution of MRSA nasal colonization to the pathogenesis of MRSA SSTI has not been defined.

Methods: In the setting of an ongoing prospective cluster-randomized trial evaluating hygiene and education measures to prevent SSTI (NCT01105767), we conducted a prospective observational cohort study in trainees with first-episode SSTI. After written informed consent, participants with SSTI underwent culture of the anterior nares to determine S. aureus colonization. Wound cultures were obtained from purulent SSTI. We determined the prevalence of S. aureus colonization in first-episode SSTI and compared colonization rates between participants with MRSA and methicillin-susceptible S. aureus (MSSA) SSTI.

Results: From May 2010 to Dec 2010 we enrolled 559 participants with SSTI. The 559 participants' mean age was 20 years; all were men.  SSTIs identified included: 183 (33%) abscesses, 213 (38%) cellulitis cases, and 163 (29%) other SSTI (e.g., folliculitis). Overall, 119 (21%) and 248 (44%) of the 559 participants were colonized with MRSA and MSSA, respectively. In participants with MRSA abscesses, 37 (37%) of 101 were simultaneously MRSA colonized, while 22 (59%) of 37 participants with MSSA abscesses were simultaneously MSSA colonized (crude OR, 2.5; 95% CI, 1.2– 5.5). In participants with any MRSA or MSSA SSTI, 58 (35%) of 165, and 59 (56%) of 105 were simultaneously colonized with MRSA and MSSA, respectively, (crude OR, 2.4; 95% CI, 1.4– 3.9). 

Conclusion: Simultaneous anterior nares colonization in first-episode SSTI appears to be less common in MRSA than MSSA SSTI. Although nasal colonization status was not assessed prior to infection, these findings suggest that exposure from other anatomical sites of colonization or extrinsic sources may play a more important role in MRSA pathogenesis. Studies are needed to examine the role of extra-nasal carriage and the importance of person-to-person and environmental modes of transmission.  

Subject Category: A. Antimicrobial agents and Resistance

Carey Schlett, MPH1, Jeffrey Lanier, MD2, James Patrick, RN3, Kenneth Wilkins, PhD4, Natasha Law, MS5, Tameka Smith, BA5, Oswald McCrory, BS6, Stephanie Morrison, MPH7, Eugene Millar, PhD8, Rachel Gorwitz, MD, MPH9, David Tribble, MD, DrPH10 and Michael Ellis, MD11, (1)Inf Dis Clin Res Prg, Uniform Serv Univ, Bethesda, MD, (2)Family Medicine, Martin Army Community Hosptial, Fort Benning, GA, (3)Infection Control, Martin Army Community Hospital, Fort Benning, GA, (4)Infectious Disease Clinical Research Program, Uniformed Services University, Bethesda, MD, (5)Infectious Disease Clinical Research Program , Fort Benning, GA, (6)Infectious Diseases Clinical Research Program, Fort Benning, GA, (7)Infectious Disease Clinical Research Program /USUHS, Bethesda, MD, (8)Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, (9)Centers for Disease Control and Prevention, Atlanta, GA, (10)IDCRP/Uniformed Services Univ. of the Hlth. Sci., Bethesda, MD, (11)Uniformed Services University of the Health Sciences, Bethesda, MD


C. Schlett, None

J. Lanier, None

J. Patrick, None

K. Wilkins, None

N. Law, None

T. Smith, None

O. McCrory, None

S. Morrison, None

E. Millar, None

R. Gorwitz, None

D. Tribble, None

M. Ellis, Forest Laboratories: Speaker's Bureau, Speaker honorarium

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.