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MRSA/SA

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The rationale for surveillance
A burdensome infection
 

In the US alone, staphylococcus aureus (SA) and methicillin resistant staphylococcus aureus (MRSA) infections burden the healthcare system with approximately $9.5 billion and $20 billion in annual care costs, respectively.1,2

Moreover, these staggering financial figures only capture a fraction of the burden attributed to MRSA and SA infections. Hospitalized patients endure prolonged stays and suffering, resulting in tangible and intangible costs that add to the considerable price tags associated with the increased morbidity and mortality rates due to MRSA/SA infections.

MRSA is a bacterial infection which causes the same infection as SA, however it is dangerous due to its resistance to many antibiotics that successfully treat normal SA. It is transmitted to an individual through bacterial contact with a wound, cut, or even ingrown hairs and razor burn on the skin’s surface. This transmission can come from the skin of another person with SA, or from a colonized environmental surface. When in the body it multiplies, invades host tissue, and causes severe inflammation and infection.3

It’s well established that SA is commonly found as part of the normal flora on the skin and in the respiratory tract of 30% of the population without negative effects on the carrier.4 However, up to 93% of hospital-acquired SA infections are caused by a patient’s own colonized flora.

The need for reliable surveillance
 

The bacteria often reside harmlessly on the body in specific locations. However, when they are displaced inside the body or into other cavities, the bacteria will begin to cause symptoms.5 Thus colonized patients, specifically, are at increased risk of developing surgical site infections, which lead to prolonged hospital stays, higher costs, and significantly increased risk of death. In fact, SA nasal carriers are 9 times more likely to develop a surgical site infection compared to non-carriers.6 Nasal carriage of SA is also a major risk factor for self-infection in dialysis, ICU, and burn patients.7

A surgical site infection related to undetected MRSA/SA results in:

  • Prolonged hospital stays
  • Increased resistance of microorganisms to antimicrobials
  • Emotional burden for patients and their families
  • Increased number of deaths

The substantial human suffering and financial burden of these endemic infections prompt an urgent need for healthcare facilities to establish effective surveillance for infection control and prevention.

All MRSA surveillance programs are not created equal
 
The most expensive program you can have is one that fails.
 

Studies point to two key parameters that determine the effectiveness of the testing methodology in helping reduce MRSA infection.8,9

  1. Sensitivity. The test methodology needs to be sufficiently sensitive to minimize the risks associated with false negatives while identifying the majority of colonized patients so that they can be managed to decrease the risk of infection and isolated to prevent spread of the pathogen.
  2. Time to intervention. Experts point to a reporting time of ≤15 hours for identifying and isolating colonized patients.8,9,10
MRSA-research
intervention-graphic
Time to intervention is critical to MRSA surveillance success11-15
 
How soon is soon enough for MRSA surveillance test results?
 

Laboratory testing time for currently available molecular methods for MRSA testing is about 1½ to 3 hours. Learn more about the Roche testing solutions.

Stat testing, whereby tests are run on demand and individual results are delivered within 2 hours, is more costly and can be beneficial only if rapid response to each and every incidence of a patient who tests positive for MRSA colonization is possible with the hospital’s current infrastructure and processes.

methodology-graphic
Choosing the test methodology16
 

MRSA surveillance testing requires an adjustment from thinking in terms of a diagnostic test (focusing on patient management) to thinking in terms of a surveillance test (addressing broader hospital- and health system–wide issues). Assessing and quantifying the impact of surveillance on infection control is critical in determining the surveillance strategy that makes the most sense for an institution.

Culture vs. Molecular
 

Culture is a well-established methodology and is used by many labs for MRSA surveillance, in part because it is perceived as inexpensive. However, to achieve a level of sensitivity equivalent to molecular methods using culture, it is necessary to perform an additional enrichment step, which increases cost and delays availability of results.

Laboratories also need to consider factors such as the lower sensitivity of culture (and missed opportunities to manage colonized patients) as well as the longer time to results (and delayed intervention), both of which can decrease the effectiveness of the surveillance program in reducing infection.

Related assays

References

 

  1. Noskin GA, Rubin RJ, Schentag JJ, et al. Budget impact analysis of rapid screening for Staphylococcus aureus colonisation among patients undergoing elective surgery in US hospitals.Infect Control Hosp Epidemiol. 2008;29(1):16-24. doi:10.1086/524327.
  2. Saadatian-Elahi M, Teyssou R, Vanhems P. Staphylococcus aureus, the major pathogen in orthopaedic and cardiac surgical site infection: a literature review.Int J Surg. 2008;6(3):238-245. doi:10.1016/j.ijsu.2007.05.001.
  3. Fraunholz, M., & Sinha, B. (2012). Intracellular staphylococcus aureus: Live-in and let die. Frontiers in Cellular and Infection Microbiology,2. doi:10.3389/fcimb.2012.00043
  4. Centers for Disease Control and Prevention. General information about MRSA in healthcare settings. http://www.cdc.gov/mrsa/healthcare/index.html. Published September 2013. Updated April 2014. Accessed April 15, 2014.
  5. Coughenour, C., Stevens, V., & Stetzenbach, L. D. (2011, September). An evaluation of methicillin-resistant Staphylococcus aureus survival on five environmental surfaces. www.ncbi.nlm.nih.gov/pubmed/21612512. Retrieved July 19, 2017.
  6. Critchley, IA. Eradication of MRSA nasal colonisation as a strategy for infection prevention. Drug Discov Today Ther Strateg. 2006;3(2):189-195. doi:10.1016/j.ddstr.2006.05.003.
  7. Yu VL, Goetz A, Wagener M, et al. Staphylococcus aureus nasal carriage and infection in patients on hemodialysis.N Engl J Med. 1986;315(2):91-96. doi:10.1056/NEJM198607103150204.
  8. Robicsek A, Beaumont JL, Paule SM, et al. Ann Intern Med 2008;148:409-418.
  9. Peterson LR, Diekema DJ. J Clin Microbiol 2010;48:683-689.
  10. Peterson LR, Karchmer T, Tenover FC. N Engl J Med 2011;365:761-762.
  11. Runz T et al. Hyg Med 2010;35:306-314.
  12. Robicsek A. al. Ann Intern Med 2008;148:409-418.
  13. Hardy K et al. Clin Microbiol Infect 2010;16:333-339.
  14. Harbath S et. Al BMJ 2008;336:927-930.
  15. Jeyaratnam D et al. BMJ 2008;336:927-930.
  16. Peterson L, Liesenfeld O, Woods CW et al. J Clin Microbiol 2010;48:1661-1666.
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