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C O N C E R N A C R O S S T H E S P E C I A L T Y S P E C T R U M MRSA Backgrounder
Overview & Brief History
MRSA (methicillin-resistant Staphylococcus aureus) is a type of bacteria that has mutated to become
much less vulnerable to the methicillin class of antibiotics (methicillin, penicillin, amoxicillin) and can
cause several types of infections, the most common of which are skin, bloodstream, and pneumonia.
These infections can be severe or even fatal if not identified and treated early and appropriately.
One of the first outbreaks of MRSA in the United States occurred at Boston City Hospital from 1967to 1968.1 By 1974, 2% of all hospital-acquired S. aureus infections were resistant to methicillin.2 By2002, 57% of ICU staph infections were caused by MRSA, and experts believe the incidence hasnow risen to 70%.3 In 2005, an estimated 94,360 people in the US contracted an infection caused by MRSA, and 18,650 of them died.4 The Changing Face of MRSA
Until recently, MRSA infections were largely confined to hospitals, with patient risk factors including
a compromised immune system, surgical wounds, or an ICU stay. Cases of MRSA are now increasing
and are now commonly seen in otherwise healthy people outside healthcare settings, with outbreaks
reported among sports teams, at health clubs, in daycare centers, and at prisons, for example.
n MRSA isolates, as a percentage of staphylococcal infections, have increased from 2% in n Even though the vast majority of MRSA infections—85%—are still found in hospitals, clusters of community-associated MRSA (CA-MRSA) have been identified6 n CA-MRSA appears to be a more virulent strain of S. aureus than the original hospital- associated strain, and CA-MRSA is now spreading inside hospitals7,8 n Public health officials have now identified a new variant of CA-MRSA, referred to as New Solutions
Most MRSA infections are treatable with antibiotics. Vancomycin has been regarded as the
“workhorse agent” for the treatment of infections caused by MRSA for nearly 50 years. However,
the decline in susceptibility to and efficacy of vancomycin has led infectious diseases experts to
seek new solutions with different mechanisms of action.
References:
1. Barrett FF, McGehee RF Jr, Finland M. Methicillin-resistant Staphylococcus aureus at Boston City Hospital: bacteriologic and epidemiologic observations. N Engl J Med. 1968;279:441-448.
2. Lauerman J. Hospitals screen for germs after Medicare threat (update 1). Bloomberg.com Web site. http://www.bloomberg.com/apps/news?pid=20670001&refer=us&sid=aZJB2.VyfO80.
Accessed April 8, 2008.
3. Keiger D. Drugs vs. bugs. Johns Hopkins Mag. http://www.jhu.edu/jhumag/0208web/drugbug.html. Accessed April 9, 2008.
4. Klevens RM, Morrison MA, Nadle J, et al; the Active Bacterial Core surveillance (ABCs) MRSA Investigators. Invasive methicillin-resistant Staphylococcus aureus infections
in the United States. JAMA. 2007;298:1763-1771.
5. Centers for Disease Control and Prevention. MRSA in healthcare settings. http://www.cdc.gov/ncidod/dhqp/ar_mrsa_spotlight_2006.html. Accessed April 8, 2008.
6. Steckelberg J. MRSA: understand your risk and how to prevent infection. http://www.mayoclinic.com/health/mrsa/ID00049. Accessed April 9, 2008.
7. UC Davis Health System. Battle of the bugs: staph infections proving to be a challenge. http://www.ucdmc.ucdavis.edu/welcome/features/20080213_medicine_mrsa/index.html.
Accessed April 9, 2008.
8. Huang H, Flynn NM, King JH, Monchaud C, Morita M, Cohen SH. Comparisons of community-associated methicillin-resistant
Staphylococcus aureus (MRSA) and hospital-associated MRSA infections in Sacramento, California. J Clin Microbiol. 2006;44:2423-2427.
9. Diep BA, Chambers HF, Graber CJ, et al. Emergence of multidrug-resistant, community-associated, methicillin-resistant
Staphylococcus aureus clone USA300 in men who have sex with men. Ann Intern Med. 2008;148:249-257.

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