Novel Assay for MRSA Detects Newly Discovered Methicillin-Resistant Strains

A newly approved molecular assay for methicillin-resistant Staphylococcus aureus (MRSA) enables more effective active surveillance of patients, improving individual patient care and reducing healthcare-associated infections (HAIs).

The BD MAX MRSA XT Assay with eXTended detection technology from BD Diagnostics, a segment of Becton, Dickinson and Company (BD; Franklin Lakes, NJ, USA), has received the CE marking and is now available in Europe for use on the BD MAX System. The assay uses eXTended detection technology to accurately identify a broad range of MRSA strains directly from nasal swabs in patients who may be colonized. It is the only automated molecular assay for MRSA active surveillance that detects a specific target found in MRSA (MREJ) and drug-resistance genes: mecA and the recently discovered mecC.


Rapid, accurate screening and thereby detection of colonized patients enables effective strategies that can help reduce the risk of surgical-site infections (SSIs) and other HAIs, improve patient safety, and save healthcare costs. With many commercial assays, Staphylococcus aureus (SA) strains carrying SCCmec where the mecA gene is absent (commonly called “dropout mutants”) are incorrectly detected as MRSA. These false positive results can lead to unnecessary and expensive isolation as well as patients being over treated. MRSA strains with the newly discovered mecC gene account for nearly 3% of all new MRSA cases but are missed by assays that do not specifically detect this gene. These false negative results can lead to lack of appropriate (e.g., vancomycin) treatment of MRSA-infected patients and to uncontrolled transmission of undetected MRSA strains.

“The new BD MAX MRSA XT assay uses eXTended detection technology to detect more MRSA strains, including the mecC gene, and to avoid false positive results due to mecA dropouts,” said Dr. Patrick Murray, Worldwide Director of Scientific Affairs, BD Diagnostics – Diagnostic Systems. More accurate detection helps focus infection prevention resources on those patients who are true MRSA carriers.

Other BD MAX System assays that help to better detect and prevent HAIs are also available, including the similar BD MAX StaphSR assay, which has recently received FDA clearance for use in the USA. StaphSR detects and differentiates SA and MRSA and is the first and currently the only commercially available molecular assay in the USA that detects the recently discovered MRSA strains with mecC. “Increased accuracy in determining patient colonization with either S. aureus or MRSA can enable clinicians to implement appropriate presurgical prophylaxis and direct appropriate utilization of isolation and decolonization,” said Dr. Tobi Karchmer, worldwide vice president, medical affairs, BD Diagnostics; “With results available in approximately 2 hours [...], the BD MAX StaphSR Assay provides accurate and timely information.”

BD MAX HAI Solutions combine efficiency with the flexibility to perform multiple HAI assays in the same run, allowing clinical laboratories to customize testing in response to current and future challenges.

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