FDA Approves First Molecular Test of Antibiotic Resistance Directly From Patient Samples

By Lori Solomon, Editor, Diagnostic Testing & Emerging Technologies

The U.S. Food and Drug Administration (FDA) recently approved the first rapid molecular test for detection of antibiotic resistance directly from patient samples.

The expanded clearance for the Xpert Carba-R assay (Cepheid; Sunnyvale, Calif.), enables rapid detection of genetic markers associated with carbapenem-resistant Enterobacteriaceae (CRE) from patient specimens. This can help hospitals and long-term care facilities identify colonized patients and aid infection control efforts.

The Xpert Carba-R assay uses real-time polymerase chain reaction technology to detect five of the most prevalent genes associated with carbapenemase, an enzyme produced by CRE. The test does not detect the bacteria itself and is one of 20 proprietary tests approved for use on the GeneXpert System.

The U.S. Centers for Disease Control and Prevention says that CRE infections most commonly occur from exposure in health care settings, such as hospitals and long-term care facilities. Patients requiring ventilators, urinary catheters or intravenous catheters, and patients who are taking long courses of certain antibiotics for severe infections are at greatest risk for CRE infections. Carbapenemase-producing organisms, commonly known as “superbugs,” are often resistant to many classes of antibiotics, posing a significant public health threat.

Cepheid received initial clearance for the Xpert Carba-R assay in March for use of the assay with pure bacterial isolates, but this expanded clearance now enables users to detect carbapenem resistance genes directly from rectal swab specimens. Traditional methods to identify colonization with CRE or other resistant organisms require growing the bacteria from fecal material in cultures, which are then subjected to antimicrobial susceptibility testing—a process that can take three to five days. But the Xpert Carba-R assay can produce results in 48 minutes, the company says.

While this marks a dramatic improvement in delivery of results that can impact patient care and the fight against antimicrobial resistance, the FDA still recommends the Xpert Carba-R Assay be used in conjunction with other tests.

“Labs should continue to perform standard bacterial culture in conjunction with the Xpert Carba-R Assay,” the FDA said in a statement. “In addition, concomitant cultures are necessary to recover organisms for epidemiological typing, antimicrobial susceptibility testing, and for confirmatory bacterial identification.”