Methicillin resistant Staphylococcus aureus

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Methicillin-resistant Staphylococcus aureus (MRSA) is a strain of Staphylococcus aureus that is resistant to commonly used antibiotics such as methicillin. MRSA emerged in the early 1960's. MRSA is predominantly a nosocomial pathogen causing hospital acquired infections as well as community acquired infections. Currently available statistics from the Kaiser foundation in 2007 indicate that about 1.2 million hospitalized patients have MRSA, and the mortality rate is estimated to be between 4%-10%.[1]

MRSA may be more virulent than other staphylococcus aureus due to carrying the gene for Panton-Valentine leucocidin (PVL). [2]

Screening for MRSA

In order to prevent the spread of the bacterium in hospitals, it would seem that patients who are infected need to be identified as soon as possible. Many antibiotics are ineffective for treating sever infections and early identification of patients is an essential precautions to take to prevent the spread.

Regarding the impact of screening:

  • A randomized controlled trial reported reduction in surgical infections by about 5%[3]
  • A cluster randomized controlled trial reported small benefits from screening in various types of hospital wards.[4] Although the authors of the trial doubted the cost of screening was justified, the authors did not conduct a formal cost analysis. Another randomized controlled trial of screening surgical patients found no benefit.[5]

As of 2008 Illinois, New Jersey, and Pennsylvania have passed laws requiring hospitals to screen certain patients upon admission for MRSA. All three states require hospitals to screen patients admitted to intensive care units and high risk patients in other parts of the hospital to identify those colonized with MRSA.[6]


Skin abscesses due to MRSA are more likely to have a central black eschar (sensitivity 55%; specificity 92%).[7]

Prevention of MRSA

See also: Cross infection

It is possible to reduce the risk of MRSA infections and transmission. Washing hands regularly, use an alcohol based hand rub, have good housekeeping skills by using disinfectants such as quaternary ammonium compounds, skin wounds should be covered with dressings to avoid exposure or isolating the infected.


Clinical practice guidelines direct management.[8]

Methicillin-resistant staphylococcus aureus is resistant to many types of antibiotics but may be treatable. Vancomycin is the most popular antibiotic used to treat infections. MRSA can also be treated teicoplanin or linezolid.[9] If the infection is community acquired MRSA and non-serious, the patient can be treated without a hospital admission using trimethoprim-sulfamethoxazole or clindamycin.

Newer drugs for resistant forms include daptomycin, a pair of streptogramin drugs used in combination: quinupristin-dalfopristin and tigecycline.


Sometimes a patient has recurrent infections caused by MRSA. Combination therapy is required if decolonization is going be attempted. Decolonization does not always work.

Side effects

The patient is being subjected to more antibiotics which could cause other factors such as elimination of indigenous flora (giving rise to Clostridium difficile pseudomembranous colitis) or development of more resistant organisms.


  1. "MRSA Infection", Medicinenet
  2. Rajendran PM, Young D, Maurer T, et al (2007). "Randomized, Double-Blind, Placebo-Controlled Trial of Cephalexin for Treatment of Uncomplicated Skin Abscesses in a Population at Risk for Community-Acquired Methicillin-Resistant Staphylococcus aureus Infection". Antimicrob. Agents Chemother. 51 (11): 4044–8. DOI:10.1128/AAC.00377-07. PMID 17846141. Research Blogging.
  3. Bode LG, Kluytmans JA, Wertheim HF, Bogaers D, Vandenbroucke-Grauls CM, Roosendaal R et al. (2010). "Preventing surgical-site infections in nasal carriers of Staphylococcus aureus.". N Engl J Med 362 (1): 9-17. DOI:10.1056/NEJMoa0808939. PMID 20054045. Research Blogging.
  4. Jeyaratnam D, Whitty CJ, Phillips K, et al (April 2008). "Impact of rapid screening tests on acquisition of meticillin resistant Staphylococcus aureus: cluster randomised crossover trial \". BMJ 336 (7650): 927–30. DOI:10.1136/bmj.39525.579063.BE. PMID 18417521. PMC 2335244. Research Blogging.
  5. Harbarth S, Fankhauser C, Schrenzel J, et al (March 2008). "Universal screening for methicillin-resistant Staphylococcus aureus at hospital admission and nosocomial infection in surgical patients". JAMA 299 (10): 1149–57. DOI:10.1001/jama.299.10.1149. PMID 18334690. Research Blogging.
  6. Infectioncontroltoday: More States Move to Require Hospitals to Screen Patients for MRSA
  7. Busch BA, Ahern MT, Topinka M, Jenkins JJ, Weiser MA (July 2008). "Eschar with cellulitis as a clinical predictor in community-acquired MRSA skin abscess". J Emerg Med. DOI:10.1016/j.jemermed.2007.11.072. PMID 18614328. Research Blogging.
  8. Liu, Catherine; Arnold Bayer, Sara E. Cosgrove, Robert S. Daum, Scott K. Fridkin, Rachel J. Gorwitz, Sheldon L. Kaplan, Adolf W. Karchmer, Donald P. Levine, Barbara E. Murray, Michael J. Rybak, David A. Talan, Henry F. Chambers. "Clinical Practice Guidelines by the Infectious Diseases Society of America for the Treatment of Methicillin-Resistant Staphylococcus Aureus Infections in Adults and Children". Clinical Infectious Diseases. DOI:10.1093/cid/ciq146. Retrieved on 2011-01-05. Research Blogging.
  9. Anonymous (2009). Drugs for MRSA with Reduced Susceptibility to Vancomycin.