Testing for MRSA in ER: Not worth bang for buck?

Enhanced focus on hand hygiene favored

When it comes to MRSA infection control in the chaotic emergency department (ED), enhanced attention to standard precautions and hand hygiene is a more cost-effective approach than active screening cultures, researchers report.

"Ours is one of the first studies to test patients in the ED for MRSA regardless of their reason for being there," says Kalpana Gupta, MD, chief of infectious diseases at the Veterans Administration Healthcare System in Boston. "While the percentage of patients who tested positive for MRSA was small — only 5% — more than half of them carried MRSA in multiple sites on their bodies. It would be very costly to make testing of all emergency patients for MRSA standard practice, but very inexpensive to institute enhanced hand washing precautions."

More than 117 million health care visits are made to EDs in the United States every year.The ED is a unique clinical environment characterized by close quarters, crowding, rapid patient turnover, and a high frequency of invasive procedures, Gupta and colleagues report.1 Additionally, comprehensive health history is often unavailable before patient contact. Prevention of transmission of infectious pathogens, particularly when they are clinically silent, is challenging in this setting, the authors emphasize.

This asymptomatic carrier state is important because it is the reservoir for MRSA transmission, which then leads to an increased risk of invasive infections in patients, as well as their close contacts. Moreover, recent reports have suggested that ED staff and health care workers have a high prevalence of asymptomatic MRSA colonization, ranging from 4.3% to 15%, they reported.2-5 In addition, the ED is frequently used by patients with complaints of skin and soft tissue infections, many of which are caused by methicillin-resistant Staphylococcus aureus (MRSA).

Gupta and colleagues performed active surveillance for methicillin-susceptible S. aureus (MSSA) and MRSA colonization on 400 adult patients across sex and all socio-economic and racial lines presenting to an urban ED. Culture testing was conducted on anterior nares, oropharynx, palms, groin, perirectal area, wounds, and catheter insertion sites. Multiplex polymerase chain reaction was used to identify the USA300 clonal types, the most predominant strain of MRSA in the community.

MRSA in multiple sites

In general, patients who tested positive for MRSA were more likely to have diabetes, be HIV positive, live in a nursing home or long-term care facility, have a recent hospitalization, have a recent incarceration in jail or play contact sports. However, 20% of the MRSA-positive subjects were otherwise healthy and had no known risk factors.

The prevalence of colonization with MSSA was 39%. The 5% prevalence of MRSA colonization found in the study more closely resembles that reported in the general ambulatory U.S. population (2%) than for health care–exposed populations (3% to 40%).5,6 The MSSA nasal colonization prevalence was also similar (22%) to that reported in the ambulatory U.S. population (29%).5 This is consistent with the fact that the study primarily included patients who presented from the community rather than institutions such as rehabilitation facilities and nursing homes. Conversely, the prevalence of extranasal colonization with MRSA and MSSA in the study was relatively high compared with that of other populations. Of the subjects with MRSA, 80% had extranasal MRSA and 45% had exclusively extranasal MRSA. That means facilities that decide to screen ED patients for MRSA colonization should consider testing other body sites in addition to nasal swabs, Gupta says.


  1. Schechter-Perkins EM, Mitchell PM, Murray KA, et al. Prevalence and predictors of nasal and extranasal staphylococcal colonization in patients presenting to the emergency department. Ann Emer Med. Published online January 18, 2011 at http://www.annemergmed.com/.
  2. Klein E, Smith DL, Laxminarayan R. Community-associated methicillin-resistant Staphylococcus aureus in outpatients, United States, 1999-2006. Emerg Infect Dis. 2009;15:1925-1930.
  3. Elie-Turenne MC, Fernandes H, Mediavilla JR, et al. Prevalence and characteristics of Staphylococcus aureus colonization among healthcare professionals in an urban teaching hospital. Infect Control Hosp Epidemiol. 2010;31:574-580.
  4. Suffoletto BP, Cannon EH, Ilkhanipour K, et al. Prevalence of Staphylococcus aureus nasal colonization in emergency department personnel. Ann Emerg Med. 2008;52:529-533.
  5. Gorwitz R, Kruszon Moran D, McAllister S, et al. Changes in the prevalence of nasal colonization with Staphylococcus aureus in the United States, 2001-2004. J Infect Dis. 2008;197:1226- 1234.
  6. Mermel LA, Eells SJ, Acharya MK, et al. Quantitative analysis and molecular fingerprinting of methicillin resistant Staphylococcus aureus nasal colonization in different patient populations: a prospective, multicenter study. Infect Control Hosp Epidemiol. 2010;31:592-597.