Biological Indicators are typically bacterial spores in a growth medium or inoculated to a spore or paper strip, which are put through the sterilization cycle intended for the drug or medical device, recovered and then checked for survivors.
Bacillus stearothermophilus: used to verify steam sterilization cycles.
Bacillus atrophaeus: used to verify peroxide sterilization cycles.
Bacillus pumilus: used to verify gamma irradiation cycles..
Incubation conditions will depend upon the organism and the manufacturer’s use instruction. A typical incubation for Bacillus stearothermophilus is 2 days at 55 – 60°C.
The Certificate of Analysis (COA) will indicate the number of spores on a Biological Indicator. The number is important in verifying the Sterility Assurance Level (SAL) of the validated process. FOCUS can confirm the spore count via validated methodologies.
The Certificate of Analysis (COA) will also indicate the D-value of the Biological Indicator. D-value is the time required to reduce the population by one log. Determining D-value requires specialized equipment such as a Bier Vessel.
An alternative to confirming the D-value is to determine the minimum expected survival and maximum expected kill time.
The minimum expected survival time = (Not Less than D Value) x (Log viable spores -2)
The maximum expected kill time = (Not more than D Value) x (Log viable spores +4)
FOCUS can verify these values.