FDA Approves New Sterilization Test for Medical Devices

The FDA recently granted permission for marketing of the Verify Cronos Self Contained Biological Indicator (SCBI), a new test that can help speed the determination of the effectiveness of steam sterilization of reusable medical devices.

According to the test’s manufacturer, Steris Corporation, the Verify Cronos SCBI is the first biological indicator test that gives test results in two hours.

“This is a novel and innovative use of recombinant DNA technology in biological indicator tests,” said Christy Foreman, director of the Office of Device Evaluation in the FDA’s Center for Devices and Radiological Health. “By providing faster confirmation of sterilization, this innovation may help health care facilities provide their medical staff with a faster turnaround of their sterilized reusable devices.”

The test is used in reprocessing—a multistep process to clean and disinfect or sterilize reusable medical devices, such as endoscopes. For steam sterilization, medical devices are loaded into a chamber that is sealed and filled with steam. Specific conditions, such as temperature, exposure time and chamber pressure, must be maintained throughout the process to kill microorganisms that may be present on the reusable medical devices.

Like other biological indicator tests, the Verify Cronos SCBI consists of a vial containing dried spores from the heat-resistant bacteria Geobacillus stearothermophilus. Before the sterilization cycle begins, the reprocessing technician places the vial inside the sterilization chamber, along with the devices to be sterilized. After the sterilization cycle is complete, the spores are incubated in “recovery medium,” a liquid that provides an ideal environment for the growth of any surviving bacteria, and monitored for spore growth. The Verify Cronos SCBI test uses a genetically engineered strain of G. stearothermophilus that produces an enzyme that fluoresces in reaction with the recovery medium if test microorganisms are present after the sterilization process. Genetically engineered G. stearothermophilus that survive a sterilization cycle will start growing and producing the enzyme within two hours, providing results to the reprocessing technicians much sooner than the 24 hours normally needed with a natural bacterial strain. Growth of bacteria indicates that sterilization has failed.

To support its FDA petition, Steris conducted a number of tests to assure the performance of the Verify Cronos SCBI. This included subjecting more than 300 Verify Cronos SCBIs to a partial sterilization cycle and then comparing results after two hours and at seven days of incubation. The results showed that samples that fluoresced at two hours also exhibited growth at seven days.

The FDA reviewed the data for Verify Cronos SCBI through the de novo classification premarket review regulatory pathway for low- to moderate-risk medical devices that are not substantially equivalent to an already legally marketed device.