New Test Could Save Valuable Time When Diagnosing MRSA

A second-generation real-time PCR assay used to determine whether a patient has a Staphylococcus aureus (SA) infection or a methicillin-resistant Staphylococcus aureus (MRSA) infection could save valuable time for patients and doctors, and help prevent the spread of antibiotic-resistant staph in the process.

Sindhu Mohandas, MD, a specialist in pediatric infectious diseases at the Montefiore Medical Center in Bronx, New York, presented research during a poster session at the 2017 Annual Pediatric Academic Societies (PAS) meeting in San Francisco, California. She and her colleagues have determined that using the Cepheid Xpert MRSA/SA Blood Culture Assay (Xpert assay) could save medical practitioners anywhere from 24 to 36 hours compared to current diagnostic methods. “This allows for optimization of treatment, some avoidance of the risk factors associated with broad-spectrum antibiotics, and potentially decreasing antibiotic resistance in the long-term,” she told Contagion®, noting that the time-saving measure may also eventually decrease cost and length of hospital stays for patients.

Dr. Mohandas and her team evaluated the Xpert assay for time to identification of infection compared to routine identification by conventional methods, MALDI and automated antimicrobial susceptibility testing (AST). “We obtained seven positive pediatric bottles from six patients over a four-week period,” she said. Dr. Mohandas also added that the cultures were tested with Xpert assay, and the results were compared to MALDI-TOF identification and BD Phoenix susceptibility testing, specifically. The team also tested 46 “spiked” bottles (23 pediatric and 23 anaerobic) that were artificially created in the lab in order to verify accuracy. “Our results showed that the Xpert assay worked for all the pediatric specimens and those created in the lab,” she said, noting that the Xpert assay’s time to presumptive identification of MRSA/SA was 27+/-10 hours compared to 68+/-7 hours for the conventional methods.

Dr. Mohandas reported that her team’s results supported those published by other teams who conducted similar studies. She added, “This method has been used in adults but, so far, not so much in pediatrics. [However], our study showed that the assay worked for pediatric specimens as well.” This is good news for doctors and patients, since when a patient enters the hospital with a potential infection, they are often immediately treated with a broad-spectrum antibiotic, Dr. Mohandas explained.

“Broad-spectrum antibiotics come with their own set of risks and complications,” she noted. “Earlier identification allows doctors to optimize treatment earlier and, furthermore, will likely reduce the length of hospital stays. The earlier we get them out of the hospital, the happier everyone is!” She added, “In some cases, the results might allow you to stop antibiotics altogether sooner than you could otherwise.”

The researchers noted that any hospital in which this test is currently available can begin using it for the purpose of distinguishing between MRSA and SA right away. “It really depends on the hospital,” said Dr. Mohandas. “Some may choose to confirm with the more commonly-used test that gives results for full antibiotic susceptibility.” She added that physicians should use the test results in conjunction with advice from an infectious disease pharmacy specialist, a pediatric infectious disease specialist, or the facility’s antimicrobial stewardship team.