FDA OKs First Test To Diagnose, Distinguish MRSA And MSSA

First test to diagnose, distinguish MRSA and MSSA is approved by FDA.

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The U.S. Food and Drug Administration has cleared the KeyPath MRSA/MSSA Blood Culture Test as the first test for Staphylococcus aureus infections that is able to identify the bacteria as methicillin resistant (MRSA) or methicillin susceptible (MSSA).

The test determines whether bacteria growing in a patient’s positive blood culture sample are MRSA or MSSA within about five hours after any bacterial growth is detected in the sample. Aside from blood culture equipment, the test does not require any specific instruments to get results. The new test was approved for human use and will not be marketed for veterinary use at this time, according to the FDA.

“This will have only limited impact on our veterinary patients,” says Anthea Schick, DVM, Dipl. ACVD, of Dermatology for Animals in Avondale, Ariz.

“This test can tell a methicillin resistant staph aureus case from a susceptible one in blood culture. Most cases of methicillin resistant staph in our veterinary patients are due to a different species of staph (Staphylococcus pseudintermedius) and most cultures we are submitting are from skin samples, ear infections and draining tracts rather than blood infections.”

The test was primarily developed with human MRSA conditions in mind, but it can have a trickle-down effect on owned animals because humans can also transfer the bacteria to pets when precautions are not taken.

“Clearing this test gives health care professionals a test that can confirm S.aureus and then identify the bacteria,” says Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostics Device Evaluation and Safety in the FDA’s Center for Devices and Radiological Health.

“This not only saves time in diagnosing potentially life-threatening infections but also allows health care professionals to optimize treatment and start appropriate contact precautions to prevent the organism’s spread.”

The FDA based its clearance on a clinical study of 1,116 blood samples evaluated at four major U.S. hospital centers. Within the organisms determined to be S.aureus, the MRSA determination was 98.9 percent accurate (178/180) and the MSSA determination was 99.4 percent accurate (153/154).

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“There are some severe cases, especially in specialty hospitals and veterinary hospitals, where we do see blood infections but these are also usually not from staph aureus, thank goodness,” Dr. Schick says. “We continue to see an amazing rise in the number of resistant staph infections in our patients and I hope to see even more advances in culture techniques and treatment options in the future.”


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