Self-contained biological indicator offers quicker method for checking effectiveness of medical device steam sterilistion
The US Food and Drug Administration (FDA) has given permission for the marketing of the Verify Cronos Self Contained Biological Indicator (SCBI), a new test that can help speed the determination of whether steam sterilisation of reusable medical devices is effective.
The first biological indicator test that gives results in two hours, the SCBI is used in reprocessing reusable medical devices.
‘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 FDA’s Center for Devices and Radiological Health. ‘By providing faster confirmation of sterilisation, this innovation may help healthcare facilities provide their medical staff with a faster turnaround of their sterilised reusable devices.’
Steam sterilisation involves loading reusable medical devices into a chamber that is sealed and filled with steam. Specific conditions such as temperature, exposure time and chamber pressure must be maintained throughout to kill micro-organisms that may be present.
Like other biological indicator tests, the Verify Cronos SCBI consists of a vial containing dried spores from the heat-resistant bacteria Geobacillus stearothermophilus. Prior to the start of a sterilisation cycle, the reprocessing technician places the vial inside the sterilisation chamber along with the sterilisation load.
After the cycle is complete, the spores are incubated in ‘recovery medium’ and monitored for spore growth. Growth of bacteria indicates that a sterilisation load failed.
The Verify Cronos SCBI test uses a genetically engineered strain, Geobacillus stearothermophilus, which produces an enzyme that fluoresces in reaction with the recovery medium if test micro-organisms are present after the sterilisation process.
Genetically engineered Geobacillus stearothermophilus that survive a sterilisation cycle will start growing and producing the enzyme within two hours, giving medical device reprocessing technicians results much faster than the 24 hours normally needed with a natural bacterial strain.
The FDA reviewed the data for Verify Cronos SCBI through the ‘de novo classification’ premarket review pathway, a regulatory pathway for low- to-moderate risk medical devices that are not substantially equivalent to an already legally marketed device.
To support the de novo petition the manufacturer conducted a number of tests to assure the performance of the Verify Cronos SCBI. This included subjecting more than 300 Verify Cronos SCBI to a partial sterilisation cycle and then comparing results after two hours and at seven days of incubation in the growth media. Results showed that samples that fluoresced at two hours also showed positive growth at seven days.
Verify Cronos SCBI is manufactured by Steris Corporation of Mentor, Ohio.