S. aureus Antibiotic Susceptibility Test to Expand FDA Clearance

A unique, accelerated-results antibiotic susceptibility test distinguishing between methicillin resistant and methicillin sensitive Staphylococcus aureus infections has entered new clinical trials to expand FDA clearance for use on additional blood culture-sample types.

The KeyPath MRSA/MSSA Blood Culture Test, produced by MicroPhage, Inc. (Longmont, CO, USA) and distributed exclusively by Cardinal Health (Dublin, OH, USA), returns same-day antibiotic susceptibility results from blood cultures known to be positive for S. aureus infections. This very simple, growth-based technique enables phenotypic measurement of bacterial response to antibiotic (cefoxitin) and provides advantages to using PCR detection alone. The new clinical trials will now examine its effectiveness on blood culture samples from the bioMérieux BacT/ALERT blood culture system. US Food and Drug Administration (FDA; Silver Spring, MD, USA) clearance for these sample types are expected to double access to the test for more than 90% of USA hospitals.


With nearly half of patients with S. aureus bloodstream infections receiving suboptimal antimicrobial therapy, the KeyPath test provides physicians with a tool that facilitates selection of safer and more effective therapy much sooner than is currently practiced. While appropriate therapy is critical for all bloodstream S. aureus patients, optimizing therapy for those with Methicillin Sensitive S. aureus (MSSA) infections has been reported to greatly reduce mortality hazards. Leading hospitals and medical centers are beginning to offer this test. Yet, while many physicians and hospitals are interested in adopting the test, many rely on significant levels of outcomes evidence to change medical practice, evidence that is typically in short supply for new technologies. “It takes innovators [...] to challenge existing thinking and adopt new and innovative products that have the potential to save lives,” said Richard Proctor, MD, professor emeritus at the University of Wisconsin Medical School and a chief advisor to MicroPhage.

MicroPhage received initial 510(k) clearance from the FDA in 2011 to market its KeyPath MRSA/MSSA Blood Culture Test. Upon issuance of the clearance, the FDA stated that the KeyPath Test, “...not only saves time in diagnosing potentially life-threatening infections but also allows health care professionals to optimize treatment...”. To date, no other tests have gained FDA clearance to report accelerated antibiotic susceptibility results. Michael Loeffelholz, PhD, and a clinical microbiology laboratory director, commented, "Never have we implemented a test so 'painless' to the laboratory, yet with the potential for such huge impact on patient care."

Related Links:
Cardinal Health
MicroPhage, Inc.
US Food and Drug Administration