FDA Clears First Rapid Diagnostic Test for Superbug MRSA

This is my health news story published last spring on GE Healthy Outlook about the first rapid diagnostic test for the highly resistant superbug MRSA.

New technology test helps fight infection sooner

FDA Clears Rapid Detection Test for MRSA

MRSA, or methicillin-resistant Staphylococcus aureus, is a superbug bacteria that is highly resistant to antibiotics like methicillin. MRSA emerged in health care settings in the 1960s, but it is now also commonly found in skin infections in the general community. A severe MRSA infection can be life threatening, especially if it develops into a bloodstream infection or pneumonia.

The FDA recently cleared the KeyPath MRSA/MSSA Blood Culture Test, the first test that can quickly identify and distinguish MRSA from MSSA (methicillin susceptible SA). This new test, manufactured by MicroPhage, can make a determination and distinction about five hours after bacterial growth is first found in a blood sample. Current test methods depend on lengthy procedures to isolate and then identify bacteria. This new test is up to two days quicker, as the Bacteriophage Amplification Technology speeds up the process while exposing the bacteria to antibiotics to determine susceptibility.

The KeyPath MRSA/MSSA Blood Culture Test was evaluated in a clinical study of 1, 116 blood samples evaluated at four major U.S. hospital centers. Within bacteria that were identified as Staphylococcus aureus, the MRSA determination was 98.9% accurate, and the MSSA determination was 99.4% accurate.

Making a quicker determination of MRSA or MSSA is critical because the mortality rate for bloodstream infections of Staphylococcus aureus is in the range of 30-40%. Right now, up to half of all suspected cases are initially prescribed suboptimal or inappropriate antibiotics until test results are available. Edward Dominguez, MD and Medical Director for Organ Transplant Infectious Diseases at the Methodist Dallas Medical Center says, “Drugs like vancomycin that we use to fight MRSA take much longer to act, about 4-5 days, compared to penicillin-class drugs which are superior to vancomycin for clearing an MSSA infection. If this test can identify the infection as an MSSA sooner, we can switch the treatment to a more targeted antibiotic earlier, and we should be able to clear the infection in 2-3 days.”

Dr. Dominguez says that doctors are looking for ways to reduce the over-use of drugs like vancomycin, as there is evidence that vancomycin-resistant strains of Staphylococcus aureus are emerging. He also points out that in the early 1900s, before antibiotics were invented, 9 out of 10 people died from bloodstream infections. Dominguez says, “A lot of people don’t realize that the upside risk of MRSA is huge. There is a 90% mortality rate if we don’t have antibiotics that are effective – it’s a deadly disease.”

A study published in the New England Journal of Medicine in 2006 found that among those adults who visited hospital emergency departments in major U.S. cities with active skin infections, 59% of them on average were infected with MRSA, and 99% of those MRSAs were community-associated MRSA types.

A MRSA skin infection can appear as a bump or infected area on the skin and may be mistaken for a spider bite. The infection may be red, swollen, painful, warm to the touch, full of pus, or accompanied by a fever. While MRSA is more prevalent than ever before, the earlier it is caught and treated, the better the outcome. Good hygiene practices can help prevent MRSA infections. The Centers for Disease Control and Prevention provides specific recommendations to help prevent MRSA infections in a variety of community settings.


Listen to a public service radio announcement about MRSA by the Department of Health and Human Services’ Centers for Disease Control and Prevention. Visit the CDC’s website to learn more about MRSA including causes, symptoms, treatment and prevention recommendations.

Originally published on GE Healthy Outlook, June 7, 2011. Copyright Jane Langille.

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