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Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Carriage in Residents of Veterans Affairs Long-Term Care Facilities: Role of Antimicrobial Exposure and MRSA Acquisition

  • Nimalie D. Stone (a1), Donna R. Lewis (a2), Theodore M. Johnson (a1) (a2), Thomas Hartney (a3), Doris Chandler (a4), Johnita Byrd-Sellers (a2), John E. McGowan (a5), Fred C. Tenover (a6), John A. Jernigan (a6) and Robert P. Gaynes (a2)...



To identify risk factors associated with methicillin-resistant Staphylococcus aureus (MRSA) acquisition in long-term care facility (LTCF) residents.


Multicenter, prospective cohort followed over 6 months.


Three Veterans Affairs (VA) LTCFs.


All current and new residents except those with short stay (<2 weeks).


MRSA carriage was assessed by serial nares cultures and classified into 3 groups: persistent (all cultures positive), intermittent (at least 1 but not all cultures positive), and noncarrier (no cultures positive). MRSA acquisition was defined by an initial negative culture followed by more than 2 positive cultures with no subsequent negative cultures. Epidemiologic data were collected to identify risk factors, and MRSA isolates were typed by pulsed-field gel electrophoresis (PFGE).


Among 412 residents at 3 LTCFs, overall MRSA prevalence was 58%, with similar distributions of carriage at all 3 facilities: 20% persistent, 39% intermittent, 41% noncarriers. Of 254 residents with an initial negative swab, 25 (10%) acquired MRSA over the 6 months; rates were similar at all 3 LTCFs, with no clusters evident. Multivariable analysis demonstrated that receipt of systemic antimicrobials during the study was the only significant risk factor for MRSA acquisition (odds ratio, 7.8 [95% confidence interval, 2.1–28.6]; P = .002). MRSA strains from acquisitions were related by PFGE to those from a roommate in 9/25 (36%) cases; 6 of these 9 roommate sources were persistent carriers.


MRSA colonization prevalence was high at 3 separate VA LTCFs. MRSA acquisition was strongly associated with antimicrobial exposure. Roommate sources were often persistent carriers, but transmission from roommates accounted for only approximately one-third of MRSA acquisitions.


Corresponding author

Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Road, Building 16, MS:A-31, Atlanta, GA 30333 (


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1. Bonomo, RA. Multiple antibiotic-resistant bacteria in long-term care facilities: an emerging problem in the practice of infectious diseases. Clin Infect Dis 2000;31:14141422.
2. Stone, ND, Lewis, DL, Lowery, HK, et al. Importance of bacterial burden among methicillin-resistant Staphylococcus aureus carriers in a long-term care facility. Infect Control Hosp Epidemiol 2008;29:143148.
3. Mulhausen, PL, Harrell, LJ, Weinberger, M, Kochersberger, GG, Feussner, JR. Contrasting methicillin-resistant Staphylococcus aureus colonization in Veterans Affairs and community nursing homes. Am J Med 1996;10:2431.
4. Mody, L, Kauffman, CA, Donabedian, S, Zervos, M, Bradley, SF. Epidemiology of Staphylococcus aureus colonization in nursing home residents. Clin Infect Dis 2008;46:13681373.
5. Davis, KA, Stewart, JJ, Crouch, HK, Florez, CE, Hospenthal, DR. Methicillin-resistant Staphylococcus aureus (MRSA) nares colonization at hospital admission and its effect on subsequent MRSA infection. Clin Infect Dis 2004;39:776782.
6. Muto, CA, Jernigan, JA, Ostrowsky, BE, et al. SHEA guideline for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus and Enterococcus . Infect Control Hosp Epidemiol 2003;24:362386.
7. Huang, SS, Yokoe, DS, Hinrichsen, VL, et al. Impact of routine intensive care unit surveillance cultures and resultant barrier precautions on hospital-wide methicillin-resistant Staphylococcus aureus bacteremia. Clin Infect Dis 2006;43:971978.
8. Tarzi, S, Kennedy, P, Stone, S, Evans, M. Methicillin-resistant Staphylococcus aureus: psychological impact of hospitalization and isolation in an older adult population. J Hosp Infect 2001; 49:250254.
9. Charlson, ME, Pompei, P, Ales, KL, MacKenzie, CR. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis 1987;40:373383.
10. McDougal, LK, Steward, CD, Killgore, GE, Chaitram, JM, McAllister, SK, Tenover, FC. Pulsed-field gel electrophoresis typing of oxacillin-resistant Staphylococcus aureus isolates from the United States: establishing a national database. J Clin Microbiol 2003;41:51135120.
11. Bradley, SF, Terpenning, MS, Ramsey, MA, et al. Methicillin-resistant Staphylococcus aureus: colonization and infection in a long-term care facility. Ann Int Med 1991;115:417422.
12. Vovko, P, Retelij, M, Cretnik, TZ, et al. Risk factors for colonization with methicillin-resistant Staphylococcus aureus in a long-term care facility in Slovenia. Infect Control Hosp Epidemiol 2005; 26:191195.
13. Mendelson, G, Yearmack, Y, Granot, E, Ben-Israel, J, Colodner, R, Raz, R. Staphylococcus aureus carrier state among elderly residents of a long term care facility. J Am Med Dir Assoc 2003;4:125127.
14. O'Sullivan, NP, Keane, CT. Risk factors for colonization with methicillin-resistant Staphylococcus aureus among nursing home residents. J Hosp Infect 2000;45:206210.
15. Wertheim, HF, Melles, DC, et al. The role of nasal carriage in Staphylococcus aureus infections. Lancet 2005;5:751762.
16. Monnet, DL. Methicillin-resistant Staphylococcus aureus and its relationship to antimicrobial use: possible implications for control. Infect Control Hosp Epidemiol 1998;19:552559.
17. Hori, S, Sunley, R, Tami, A, Grundmann, H. The Nottingham Staphylococcus aureus population study: prevalence of MRSA among elderly in a university hospital. J Hosp Infect 2002;50: 2529.
18. Graffunder, EM, Venezia, RA. Risk factors associated with nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection including previous use of antimicrobials. J Antimicrob Chemo 2002;49:9991005.
19. Dziekan, G, Hahn, A, Thune, K, et al. Methicillin-resistant Staphylococcus aureus in a teaching hospital: investigation of nosocomial transmission using a matched case-control study. J Hosp Infect 2000;46:263270.
20. Moore, C, Dhaliwal, J, Tong, A, et al. Risk factors for methicillin-resistant Staphylococcus aureus (MRSA) acquisition in roommate contacts of patients colonized or infected with MRSA in an acute-care hospital. Infect Control Hosp Epidemiol 2008;29: 600606.
21. van Belkum, A, Verkaik, NJ, de Vogel, CP, et al. Reclassification of Staphylococcus aureus nasal carriage types. J Infect Dis 2009; 199:18201826.
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Infection Control & Hospital Epidemiology
  • ISSN: 0899-823X
  • EISSN: 1559-6834
  • URL: /core/journals/infection-control-and-hospital-epidemiology
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