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Prevalence of USA300 Strain Type of Methicillin-Resistant Staphylococcus aureus among Patients with Nasal Colonization Identified with Active Surveillance

  • Eduardo A. F. Freitas (a1), Rebecca M. Harris (a2), Ruth K. Blake (a1) and Cassandra D. Salgado (a1)



USA300 is the most prevalent strain type of community-acquired methicillin-resistant Staphylococcus aureus (MRSA), but the proportion of patients colonized with USA300 strains and their risk for infection are largely unknown.


To determine the prevalence of USA300 strains among MRSA nasal colonizing isolates in our hospital, to identify risks for USA300 nasal colonization, and to determine risks of developing infection for nasally colonized patients.


Retrospective cohort study of patients found to be nasally colonized with MRSA through active surveillance at a tertiary care hospital from January 2005 through December 2007. MRSA isolates were identified as USA300 or non-USA300. Risks for colonization and infection were identified with logistic regression.


Among 1,306 MRSA nasal isolates, 307 (24%) were USA300 strains, and this proportion significantly increased over time (17.4% in 2005 and 26.7% in 2007; P = .003). African American race was an independent risk for USA300 nasal colonization (odds ratio [OR], 1.81 [95% confidence ratio {CI}, 1.38-2.38]). Older age (OR, 0.97 [95% CI, 0.96-0.98]) and female sex (OR, 0.74 [95% CI, 0.56-0.97]) decreased risk. Among nasally colonized patients, 238 (18.2%) developed infection. Increased length of stay (OR, 1.03 [95% CI, 1.01-1.06]) independently increased risk for infection among patients nasally colonized with USA300 MRSA, and female sex decreased risk (OR, 0.48 [95% CI, 0.24-0.95]). Increased length of stay (OR, 1.03 [95% CI, 1.02-1.04]) and treatment in an intensive care unit (OR, 1.64 [95% CI, 1.10-2.44]) independently increased risk for infection among patients nasally colonized with non-USA300 MRSA, and female sex decreased risk (OR, 0.67 [95% CI, 0.47-0.94]).


The proportion of MRSA nasally colonized patients with USA300 strains significantly increased during the study, and risks included African American race. Strain type had no significant effect on the proportion of patients who developed infection, and risk factors for infection were similar.


Corresponding author

Department of Medicine, 135 Rutledge Avenue, 12th Floor RT, Charleston, SC 29425, (


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1.Barber, M. Methicillin-resistant staphylococci. J Clin Pathol 1961;14(4): 385393.
2.Burton, DC, Edwards, JR, Horan, TC, Jernigan, JA, Fridkin, SK. Methicillin-resistant Staphylococcus aureus central line-associated bloodstream infections in US intensive care units, 1997-2007. JAMA 2009;301(7):727736.
3.Thompson, DS, Workman, R, Strutt, M. Contribution of acquired methicillin-resistant Staphylococcus aureus bacteraemia to overall mortality in a general intensive care unit. J Hosp Infect 2008;70(3):223227.
4.Ben-David, D, Novikov, I, Mermel, LA. Are there differences in hospital cost between patients with nosocomial methicillin-resistant Staphylococcus aureus bloodstream infection and those with methicillin-susceptible S. aureus bloodstream infection? Infect Control Hosp Epidemiol 2009;30(5):453460.
5.Cosgrove, SE, Qi, Y, Kaye, KS, Harbarth, S, Karchmer, AW, Carmeli, Y. The impact of methicillin resistance in Staphylococcus aureus bacteremia on patient outcomes: mortality, length of stay, and hospital charges. Infect Control Hosp Epidemiol 2006;27(9):994995.
6.Klein, E, Smith, DL, Laxminarayan, R. Hospitalizations and deaths caused by methicillin-resistant Staphylococcus aureus, United States, 1999-2005. Emerg Infect Dis 2007;13(12):18401846.
7.Centers for Disease Control and Prevention. Four pediatric deaths from community-acquired methicillin-resistant Staphylococcus aureus—Minnesota and North Dakota, 1997-1999. JAMA 1999;282(12):11231125.
8.King, MD, Humphrey, BJ, Wang, YF, Kourbatova, EV, Ray, SM, Blumberg, HM. Emergence of community-acquired methicillin-resistant Staphylococcus aureus USA 300 clone as the predominant cause of skin and soft-tissue infections. Ann Intern Med 2006;144(5):309317.
9.Al-Rawahi, GN, Reynolds, S, Porter, SD, et al.Community-associated CMRSA-10 (USA-300) is the predominant strain among methicillin-resistant Staphylococcus aureus strains causing skin and soft tissue infections in patients presenting to the emergency department of a Canadian tertiary care hospital. J Emerg Med 2010;38(1):611.
10.Moran, GJ, Krishnadasan, A, Gorwitz, RJ, et al.Methicillin-resistant S. aureus infections among patients in the emergency department. N Engl J Med 2006;355(7):666674.
11.Kaplan, SL, Hulten, KG, Gonzalez, BE, et al.Three-year surveillance of community-acquired Staphylococcus aureus infections in children. Clin Infect Dis 2005;40(12):17851791.
12.Hidron, AI, Low, CE, Honig, EG, Blumberg, HM. Emergence of community-acquired methicillin-resistant Staphylococcus aureus strain USA300 as a cause of necrotizing community-onset pneumonia. Lancet Infect Dis 2009;9(6):384392.
13.Vayalumkal, JV, Whittingham, H, Vanderkooi, O, et al.Necrotizing pneumonia and septic shock: suspecting CA-MRSA in patients presenting to Canadian emergency departments. CJEM 2007;9(4):300303.
14.Kefala-Agoropoulou, K, Protonotariou, E, Vitti, D, et al.Life-threatening infection due to community-acquired methicillin-resistant Staphylococcus aureus: case report and review. Eur J Pediatr 2010;169(1):4753.
15.Klevens, RM, Morrison, MA, Nadle, J, et al; Active Bacterial Core surveillance (ABCs) MRSA Investigators. Invasive methicillin-resistant Staphylococcus aureus infections in the United States. JAMA 2007;298(15): 17631771.
16.Seybold, U, Kourbatova, EV, Johnson, JG, et al.Emergence of community-associated methicillin-resistant Staphylococcus aureus USA300 genotype as a major cause of health care-associated blood stream infections. Clin Infect Dis 2006;42(5):647656.
17.Patel, M, Kumar, RA, Stamm, AM, Hoesley, CJ, Moser, SA, Waites, KB. USA300 genotype community-associated methicillin-resistant Staphylococcus aureus as a cause of surgical site infections. J Clin Microbiol 2007;45:34313433.
18.Liu, C, Graber, CJ, Karr, M, et al.A population-based study of the incidence and molecular epidemiology of methicillin-resistant Staphylococcus aureus disease in San Francisco, 2004-2005. Clin Infect Dis 2008;46:16371646.
19.Huang, SS, Platt, R. Risk of methicillin-resistant Staphylococcus aureus infection after previous infection or colonization. Clin Infect Dis 2003;36(3): 281285.
20.Tenover, FC, Arbeit, RD, Goering, RV, et al.Interpreting chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing. J Clin Microbiol 1995;33(9):22332239.
21.Gorwitz, RJ, Kruszon-Moran, D, McAllister, SK, et al.Changes in the prevalence of nasal colonization with Staphylococcus aureus in the United States, 2001-2004. J Infect Dis 2008;197(9):12261234.
22.Shurland, SM, Stine, OC, Venezia, RA, et al.Colonization sites of USA300 methicillin-resistant Staphylococcus aureus in residents of extended care facilities. Infect Control Hosp Epidemiol 2009;30(4):313318.
23.Hidron, AI, Kourbatova, EV, Halvosa, JS, et al.Risk factors for colonization with methicillin-resistant Staphylococcus aureus (MRSA) in patients admitted to an urban hospital: emergence of community-associated MRSA nasal carriage. Clin Infect Dis 2005;41(2):159166.
24.Carleton, HA, Diep, BA, Charlebois, ED, Sensabaugh, GF, Perdreau-Rem-ington, F. Community-adapted methicillin-resistant Staphylococcus aureus (MRSA): population dynamics of an expanding community reservoir of MRSA. J Infect Dis 2004;190:17301738.
25.Benoit, SR, Estivariz, C, Mogdasy, C, et al.Community strains of methicillin-resistant Staphylococcus aureus as potential cause of healthcare-associated infections, Uruguay, 2002-2004. Emerg Infect Dis 2008;14(8): 12161223.
26.Patel, M, Waites, K, Hoesley, C, Stamm, A, Canupp, K, Moser, S. Emergence of USA300 MRSA in a tertiary medical centre: implications for epidemiological studies. J Hosp Infect 2008;68(3): 208213.
27.Kaplan, SL, Hulten, KG, Gonzalez, BE, et al.Three-year surveillance of community-acquired Staphylococcus aureus infections in children. Clin Infect Dis 2005;40(12):17851791.
28.Saiman, L, O'Keefe, M, Graham, PL III, et al.Hospital transmission of community-acquired methicillin-resistant Staphylococcus aureus among postpartum women. Clin Infect Dis 2003;37(10):13131319.
29.Naimi, TS, LeDell, KH, Boxrud, DJ, et al.Epidemiology and clonality of community-acquired methicillin-resistant Staphylococcus aureus in Minnesota, 1996-1998. Clin Infect Dis 2001;33(7):990996.
30.Naimi, TS, LeDell, KH, Como-Sabetti, K, et al.Comparison of community-and healthcare-associated, methicillin-resistant Staphylococcus aureus infection. JAMA 2003;290:29762984.
31. US Census Bureau. Census 2000 data for the state of South Carolina. U.S. Census Bureau Web site, Accessed June 25, 2009.
32.Davis, SL, Perri, MB, Donabedian, SM, et al.Epidemiology and outcomes of community-associated methicillin-resistant Staphylococcus aureus infection. J Clin Microbiol 2007;45(6):17051711.
33.Miller, LG, Diep, BA. Clinical practice: colonization, fomites, and virulence: rethinking the pathogenesis of community-associated methicillin-resistant Staphylococcus aureus infection. Clin Infect Dis 2008;46:752760.


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