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Newsletter Vol. 29 No. 2




Next Generation MRSA Screening: an interview with Molecular Detection Inc.



Tzvi Tzubery, Ph.D.
Director of Research and Development
Molecular Detection Inc.





Molecular Detection Inc. (MDI) is developing and commercializing a portfolio of sample-to-answer Detect-Ready® molecular diagnostic tests for the rapid detection of infectious diseases. MDI recently launched the Detect-Ready MRSA Panel in major European countries and Australia for the rapid diagnosis of MRSA and related infections.

Why is MRSA screening in hospitals important? What is the scope of the problem currently facing healthcare facilities?

Hospital acquired infections (HAIs) are an increasing problem, with infection from the highly contagious MRSA (methicillin-resistant staphylococcus aureus) bacteria among the most prevalent. MRSA bacteria are resistant to all but the most powerful broad-spectrum antibiotics. The Centers for Disease Control (CDC) estimates that in 2008, there were approximately 90,000 persons in the U.S. diagnosed with a MRSA infection, and an estimated 15,000 patients died [1]. Until recently, the incidence of MRSA and MSSA (methicillin-sensitive S. aureus) infections had been rising, but recent evidence suggests that active surveillance (screening) programs, along with other infection control measures, have been effective in reducing MRSA infection rates [2].

The S. aureus pathogen can be spread by medical personnel, medical instruments, or from exposure to bacteria on furniture or other surfaces. Routine invasive medical procedures create openings for MRSA and MSSA to enter the bloodstream, and hospitalized patients can have weakened immune systems that put them at increased risk. Once a bloodstream infection is established, it can result in serious illness and death, while lengthening hospital stays and increasing medical costs.

What are the costs involved with MRSA and other HAIs?
The costs are high in both human and monetary terms. Researchers have estimated that it costs $3.2 - $4.2 billion annually to treat MRSA in hospitalized patients in the U.S. [3]. Duke University researchers estimate that a surgical patient infected with MRSA increases hospital costs by more than $61,000, and a surgical patient with a MSSA infection increases hospital costs by over $24,000. These researchers also found a seven-fold increased risk of death within 90 days for patients who developed MRSA-related surgical site infections as compared to those who did not [4].

The high costs of these infections are leading healthcare payors to implement financial penalties to provide incentives for achieving better control. Both the Medicare and Medicaid programs have been experimenting with imposing financial penalties on hospitals for above average rates of HAIs and other adverse events. Both programs are already withholding some payments for excessive HAIs and private insurers are instituting similar programs.

How can MRSA screening programs help diminish the infection rate?
Successful MRSA control efforts employ a variety of measures. Among the interventions that are credited with helping to achieve the recent decreases in MRSA infection rates are programs aimed at screening potential carriers. Rapid diagnostic screening to identify carriers of MRSA and MSSA pathogens at the time of patient admission aids in effective control by enabling special precautions to be used with infected patients, their facilities and the personnel who care for them.

A study published in the New England Journal of Medicine earlier this year reported a 62% reduction in MRSA infection rates in ICUs in 153 acute care VA hospitals over a four-year period following the implementation of a “MRSA bundle,” which included universal nasal screening for MRSA [2]. The National Health Service in the UK has implemented a universal screening policy for MRSA and in June this year reported the lowest-ever level of MRSA infection in its hospitals [6].

Are new generation diagnostic tests making MRSA screening programs more feasible? More effective?
The MRSA pathogen traditionally has been identified using bacterial culture techniques that require at least two days for results, during which time the bacteria can spread through the facility. A number of molecular diagnostic MRSA assays that provide test results more quickly have become available in recent years, and they have the potential to make MRSA screening far more feasible. A screening test that distinguishes between MRSA, MSSA, methicillin-resistant non-S. aureus pathogens and mixed samples is particularly important for physicians making treatment decisions in the hospital setting, where these infections are most likely to be serious and potentially lethal. We are seeing an increasing number of clinicians at the facilities we serve wanting to know if a patient is at risk for MSSA as well as MRSA. This capacity has also been highlighted by the FDA, which deemed the capability to distinguish MRSA, MSSA and other S. aureus pathogens essential [7].

Molecular Detection Inc. (MDI) is developing a portfolio of sample-to-answer Detect-Ready® molecular diagnostic tests for the rapid detection of antibiotic- resistant bacteria such as MRSA. The system will incorporate unique technology that analyzes multiple gene targets to produce highly accurate results, minimizing the false positives and false negatives that have limited the utility of some molecular diagnostic assays. Additionally, it can be run on a number of popular diagnostic platforms, affording hospitals maximum flexibility and minimizing the need to invest in expensive equipment.
 




References
1. Centers for Disease Control and Prevention. Active Bacterial Core Surveillance Report, Methicillin-Resistant Staphylococcus aureus. 2008. Retrieved Aug. 11, 2011 from http://www.cdc.gov/abcs/reports-findings/survreports/mrsa08.html.
2. Jain R., Kralovic S.M., Evans M.E., Ambrose M., Simbartl L.A., Obrosky D.S., Render M.L., Freyberg R.W., Jernigan J.A., Muder R.R., Miller L.J., Roselle G.A. Veterans Affairs Initiative to Prevent Methicillin-Resistant Staphylococcus aureus Infections. N Engl J Med. 2011 Apr 14. 364:1419-30. http://www.nejm.org/doi/full/10.1056/NEJMoa1007474
3. Pfizer Inc. New research estimates MRSA infections cost U.S. hospitals $3.2 billion to $4.2 billion annually. Infection Control Today. 2005. Available at http://www.infectioncontroltoday.com/hotnews/55h168584264313.html
4. Engemann J.J., Carmeli Y., Cosgrove S.E., Fowler V.G. Jr., Bronstein M.Z., Trivette S.L., Briggs J.P., Sexton D.J. Adverse Clinical and Economic Outcomes Attributable to Methicillin Resistance among Patients with Staphylococcus aureus Surgical Site Infection. Clin Infect Dis. 2003 Mar 1;36(5):592-8. http://cid.oxfordjournals.org/content/36/5/592.full.
5. Health Protection Agency. Results from the mandatory surveillance of meticillin resistant Staphylococcus aureus (MRSA) bacteraemia. 2011. Retrieved Aug. 12, 2011 from http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/StaphylococcusAureus/EpidemiologicalData/MandatorySurveillance/staphmonthlymandatoryreporting/
6. Draft Guidance for Industry and Food and Drug Administration (FDA) Staff - Establishing the Performance Characteristics of Nucleic Acid-Based In vitro Diagnostic Devices for the Detection and Differentiation of Methicillin-Resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus (SA). 2011. Retrieved February 7, 2011 from http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm237235.htm




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